fix(group)!: remove max_candidates_per_step and shared_libs (U6)

Both keys were declared, defaulted, written into every generated group.yaml,
and read by nothing -- the same three-station dead surface this PR removed for
bm25_threshold, embedding_threshold and detect.embedding_fallback. Every other
DetectConfig field gates a real extractor in sync.ts; shared_libs gates nothing,
because 'lib' contracts come only from the operator-declared manifest extractor.
MatchingConfig reaches matching.ts solely through buildNoisyContractFilter,
which reads exclude_links_paths and exclude_links_param_only_paths and nothing
else.

Existing group.yaml files keep loading and keep their keys. parseGroupConfig
spreads the raw block over its defaults, so a key the schema no longer knows
about survives into the returned config -- which matters because `group add` and
`group remove` round-trip the operator's file through loadGroupConfig ->
yaml.dump -> write, so anything the parser dropped would be deleted from their
checked-in file. The legacy-config test now pins both keys in the same cast form
as its three siblings, and the fixture carries shared_libs so that assertion is
not vacuous.

Two stations that are easy to miss and are swept here:

- gitnexus/bench/cross-repo-trace/verify.mjs GENERATES a fresh group.yaml. It is
  not a preserve-path fixture, so "leave YAML fixtures alone" does not cover it;
  the repo has two generators and both are updated. It is a .mjs file outside
  tsconfig's include, so no type gate would have caught it.
- config-parser.test.ts asserted the removed default at runtime, which vitest
  DOES run. That assertion is gone from the defaults case (the key no longer has
  a default) and re-formed as a preserve assertion in the legacy case.

Verification gate, corrected: "zero net new errors against origin/main" would
have measured the whole branch delta and been red through no fault of this
commit. Measured instead against the branch tip immediately before it --
tsc -p tsconfig.test.json --noEmit reports 989 before and 989 after. Twenty-four
typed-literal sites across ten test files, none of them CI-gated, plus the two
runtime sites above which are.

Note the deliberate side effect: removing a key from the defaults also stops the
group add round-trip from re-adding it to a file that never carried it. Nothing
in src reads either key, so no behavior changes.

BREAKING CHANGE: `matching.max_candidates_per_step` and `detect.shared_libs` are
no longer part of the group.yaml schema and are no longer written into generated
templates. Existing files carrying them continue to parse and retain them.

src tsc clean; 1189/1189 across the group unit, group integration, locale-parity,
help-registration and tool-schema suites.

gitnexus/bench/cross-repo-trace/verify.mjs

@@ -58,7 +58,6 @@ packages: {}
 detect:
   http: true
 matching:
-  max_candidates_per_step: 3
 `;
 }
 

gitnexus/src/core/group/config-parser.ts

@@ -29,13 +29,11 @@ const DEFAULT_DETECT = {
   grpc: true,
   thrift: true,
   topics: true,
-  shared_libs: true,
   includes: false,
   workspace_deps: false,
 };
 
 const DEFAULT_MATCHING = {
-  max_candidates_per_step: 3,
   exclude_links_paths: [] as string[],
   exclude_links_param_only_paths: false,
 };

gitnexus/src/core/group/storage.ts

@@ -98,10 +98,8 @@ detect:
   http: true
   grpc: true
   topics: true
-  shared_libs: true
 
 matching:
-  max_candidates_per_step: 3
   # exclude_links_paths: [/ping, /health, /healthcheck]
   # exclude_links_param_only_paths: false
 `;

gitnexus/src/core/group/types.ts

@@ -26,13 +26,11 @@ export interface DetectConfig {
   grpc: boolean;
   thrift: boolean;
   topics: boolean;
-  shared_libs: boolean;
   includes: boolean;
   workspace_deps: boolean;
 }
 
 export interface MatchingConfig {
-  max_candidates_per_step: number;
   /**
    * HTTP paths to exclude from cross-link matching. Contracts at these paths
    * are still extracted and visible in the registry, but they don't produce

gitnexus/test/integration/group/group-sync-lock-concurrency.test.ts

@@ -51,11 +51,10 @@ const makeConfig = (name: string): GroupConfig => ({
     grpc: false,
     thrift: false,
     topics: false,
-    shared_libs: false,
     includes: false,
     workspace_deps: false,
   },
-  matching: { max_candidates_per_step: 3 },
+  matching: {},
 });
 
 const parentContract: StoredContract = {

gitnexus/test/unit/group/config-parser.test.ts

@@ -59,7 +59,6 @@ repos:
     expect(config.links).toEqual([]);
     expect(config.packages).toEqual({});
     expect(config.detect.http).toBe(true);
-    expect(config.matching.max_candidates_per_step).toBe(3);
     expect(config.matching.exclude_links_paths).toEqual([]);
     expect(config.matching.exclude_links_param_only_paths).toBe(false);
   });
@@ -77,6 +76,7 @@ repos:
 detect:
   http: true
   embedding_fallback: true
+  shared_libs: true
 matching:
   bm25_threshold: 0.7
   embedding_threshold: 0.65
@@ -86,7 +86,6 @@ matching:
     expect(config.name).toBe('test');
     expect(config.repos).toEqual({ app: 'my-app' });
     expect(config.detect.http).toBe(true);
-    expect(config.matching.max_candidates_per_step).toBe(3);
 
     // Pinned behavior: PRESERVE, not strip. The parser spreads the raw block
     // over its defaults (`{ ...DEFAULT_MATCHING, ...raw.matching }`), so a key
@@ -102,6 +101,11 @@ matching:
     expect((config.matching as unknown as Record<string, unknown>).bm25_threshold).toBe(0.7);
     expect((config.matching as unknown as Record<string, unknown>).embedding_threshold).toBe(0.65);
     expect((config.detect as unknown as Record<string, unknown>).embedding_fallback).toBe(true);
+    // The two keys this commit removes, pinned the same way and for the same
+    // reason: an operator's group.yaml carries them today because
+    // `gitnexus group create` wrote them there.
+    expect((config.matching as unknown as Record<string, unknown>).max_candidates_per_step).toBe(3);
+    expect((config.detect as unknown as Record<string, unknown>).shared_libs).toBe(true);
   });
 
   it('defaults thrift detection to true', () => {

gitnexus/test/unit/group/matching.test.ts

@@ -636,7 +636,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('exclude_links_paths prevents cross-links for configured paths', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: ['/ping'],
       exclude_links_param_only_paths: false,
     };
@@ -657,7 +656,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('excluded providers do not appear in matched', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: ['/health'],
       exclude_links_param_only_paths: false,
     };
@@ -675,7 +673,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('excluded contracts do not appear in unmatched', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: ['/ping'],
       exclude_links_param_only_paths: false,
     };
@@ -694,7 +691,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('exclude_links_param_only_paths filters /{param} and /{param}/{param}', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: [],
       exclude_links_param_only_paths: true,
     };
@@ -715,7 +711,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('mixed routes like /users/{param} are NOT excluded by param_only', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: [],
       exclude_links_param_only_paths: true,
     };
@@ -747,7 +742,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('trailing slash on contractId still matches configured exclusion', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: ['/ping'],
       exclude_links_param_only_paths: false,
     };
@@ -766,7 +760,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('root path exclusion ["/"] suppresses http::GET::/ contracts', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: ['/'],
       exclude_links_param_only_paths: false,
     };
@@ -788,7 +781,6 @@ describe('buildNoisyContractFilter (via runExactMatch)', () => {
 
   it('non-HTTP contracts are never filtered', () => {
     const matchingConfig: MatchingConfig = {
-      max_candidates_per_step: 3,
       exclude_links_paths: ['/ping'],
       exclude_links_param_only_paths: true,
     };

gitnexus/test/unit/group/registry-suppressed-stages.test.ts

@@ -40,12 +40,10 @@ const config: GroupConfig = {
     grpc: false,
     thrift: false,
     topics: false,
-    shared_libs: false,
     includes: false,
     workspace_deps: false,
   },
   matching: {
-    max_candidates_per_step: 3,
     exclude_links_paths: [],
     exclude_links_param_only_paths: false,
   },

gitnexus/test/unit/group/sync-exact-only.test.ts

@@ -28,11 +28,10 @@ describe('syncGroup exactOnly gates the wildcard stage', () => {
       grpc: false,
       thrift: false,
       topics: false,
-      shared_libs: false,
       includes: false,
       workspace_deps: false,
     },
-    matching: { max_candidates_per_step: 3 },
+    matching: {},
   };
 
   /**

gitnexus/test/unit/group/sync-partial-extraction.test.ts

@@ -92,11 +92,10 @@ const config = (): GroupConfig => ({
     grpc: true,
     thrift: false,
     topics: false,
-    shared_libs: false,
     includes: false,
     workspace_deps: false,
   },
-  matching: { max_candidates_per_step: 3 },
+  matching: {},
 });
 
 describe('syncGroup when one extractor fails partway through a repo', () => {

gitnexus/test/unit/group/sync-unreadable-repos.test.ts

@@ -169,11 +169,10 @@ const makeConfig = (repos: Record<string, string>): GroupConfig => ({
     grpc: false,
     thrift: false,
     topics: false,
-    shared_libs: false,
     includes: false,
     workspace_deps: false,
   },
-  matching: { max_candidates_per_step: 3 },
+  matching: {},
 });
 
 /**

gitnexus/test/unit/group/sync-windowed-resolution.test.ts

@@ -213,11 +213,10 @@ describe('syncGroup windowed resolution bounds pool residency (real pool, #2189)
         grpc: false,
         thrift: false,
         topics: false,
-        shared_libs: false,
         includes: false,
         workspace_deps: false,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
 
     await syncGroup(config, {

gitnexus/test/unit/group/sync.test.ts

@@ -26,11 +26,10 @@ describe('syncGroup', () => {
       grpc: false,
       thrift: false,
       topics: false,
-      shared_libs: false,
       includes: false,
       workspace_deps: false,
     },
-    matching: { max_candidates_per_step: 3 },
+    matching: {},
   });
 
   it('returns SyncResult with contracts and cross-links', async () => {
@@ -222,11 +221,10 @@ describe('syncGroup', () => {
         grpc: false,
         thrift: false,
         topics: false,
-        shared_libs: false,
         includes: false,
         workspace_deps: false,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
 
     const result = await syncGroup(config, {
@@ -676,11 +674,10 @@ service OrderService {
         grpc: false,
         thrift: false,
         topics: false,
-        shared_libs: false,
         includes: false,
         workspace_deps: false,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
 
     const cap = _captureLogger();
@@ -746,11 +743,10 @@ service OrderService {
           grpc: false,
           thrift: false,
           topics: false,
-          shared_libs: false,
           includes: false,
           workspace_deps: workspaceDeps,
         },
-        matching: { max_candidates_per_step: 3 },
+        matching: {},
       };
     }
 
@@ -903,11 +899,10 @@ service OrderService {
           grpc: false,
           thrift: false,
           topics: false,
-          shared_libs: false,
           includes: false,
           workspace_deps: true,
         },
-        matching: { max_candidates_per_step: 3 },
+        matching: {},
       };
 
       const result = await syncGroup(config, {
@@ -994,11 +989,10 @@ service OrderService {
         grpc: false,
         thrift: false,
         topics: false,
-        shared_libs: false,
         includes: false,
         workspace_deps: false,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
 
     const poolAdapter = await import('../../../src/core/lbug/pool-adapter.js');
@@ -1078,11 +1072,10 @@ service OrderService {
         grpc: false,
         thrift: false,
         topics: false,
-        shared_libs: false,
         includes: false,
         workspace_deps: false,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
 
     const result = await syncGroup(config, {
@@ -1122,11 +1115,10 @@ describe('syncGroup windowed manifest resolution (issue #2189 / PR #2191 review)
         grpc: false,
         thrift: false,
         topics: false,
-        shared_libs: false,
         includes: false,
         workspace_deps: false,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
   };
 

gitnexus/test/unit/group/types.test.ts

@@ -23,11 +23,10 @@ describe('Group types', () => {
         grpc: true,
         thrift: true,
         topics: true,
-        shared_libs: true,
         includes: true,
         workspace_deps: true,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
     expect(config.version).toBe(1);
     expect(config.name).toBe('company');
@@ -92,11 +91,10 @@ describe('Group types', () => {
         grpc: true,
         thrift: true,
         topics: true,
-        shared_libs: true,
         includes: true,
         workspace_deps: true,
       },
-      matching: { max_candidates_per_step: 3 },
+      matching: {},
     };
     expect(config.detect.thrift).toBe(true);
   });

gitnexus/test/unit/repo-manager-registry-strict-read.test.ts

@@ -68,11 +68,10 @@ describe('readRegistryStrict', () => {
       grpc: false,
       thrift: false,
       topics: false,
-      shared_libs: false,
       includes: false,
       workspace_deps: false,
     },
-    matching: { max_candidates_per_step: 3 },
+    matching: {},
   });
 
   beforeEach(async () => {