fix(r): flag an unreadable DESCRIPTION as truncated and tighten three R test assertions

An unreadable DESCRIPTION left RPackageConfig.truncated false, so a
qualifier naming the package it declares was classed external and its
call site dropped. The sibling hidesUndiscoveredPackage case already
treats an unreadable DESCRIPTION as unknown; do the same here and cover
it with a test.

Tighten three weak test assertions: the escaped-bracket export pattern
now asserts its exact match results, the S4 anchors test proves each
generic is defined exactly once, and the worker owner-absence test
fails on any defined ownerId, including an empty string.

gitnexus/src/core/ingestion/languages/r/package-config.ts

@@ -383,7 +383,8 @@ export async function loadRPackageConfig(repoRoot: string): Promise<RPackageConf
               }
             }
           } catch {
-            // Can't read DESCRIPTION
+            // Can't read DESCRIPTION: the package it declares was not discovered.
+            truncated = true;
           }
         }
       }

gitnexus/test/integration/r-worker-owner-absence.test.ts

@@ -74,7 +74,7 @@ describe.skipIf(!hasDistWorker)('R worker never emits an owner id (before post-p
       let hintedMembers = 0;
       graph.forEachNode((n) => {
         if (n.properties.language !== 'r') return;
-        if (typeof n.properties.ownerId === 'string') ownedNodes++;
+        if (n.properties.ownerId !== undefined) ownedNodes++;
         if (
           (n.label === 'Method' || n.label === 'Property') &&
           typeof n.properties.ownerNameHint === 'string'
@@ -88,7 +88,7 @@ describe.skipIf(!hasDistWorker)('R worker never emits an owner id (before post-p
       for (const result of raw) {
         for (const symbol of result.symbols) {
           symbols++;
-          if (symbol.ownerId) ownedSymbols++;
+          if (symbol.ownerId !== undefined) ownedSymbols++;
         }
       }
 

gitnexus/test/integration/resolvers/r-s4-anchors.test.ts

@@ -58,8 +58,8 @@ describe('R S4/RefClass definitions are named by their first argument only', ()
 
   it('defines the generics once, with no Function from valueClass = "numeric"', () => {
     const functions = getNodesByLabel(result, 'Function');
-    expect(functions).toContain('describe');
-    expect(functions).toContain('summarise');
+    expect(functions.filter((n) => n === 'describe')).toHaveLength(1);
+    expect(functions.filter((n) => n === 'summarise')).toHaveLength(1);
     expect(functions).not.toContain('numeric');
   });
 

gitnexus/test/unit/r-export-pattern.test.ts

@@ -73,6 +73,12 @@ describe('compileRExportPattern', () => {
   });
 
   it('does not treat an escaped bracket as a bracket expression', () => {
+    // `\[` is a literal bracket; the rest is an ordinary one-character class of `:alph`,
+    // so the pattern compiles (to itself) and matches `[` plus exactly one of those characters.
+    expect(compileRExportPattern('^\\[[:alpha:]$')?.source).toBe('^\\[[:alpha:]$');
+    expect(matches('^\\[[:alpha:]$', '[a')).toBe(true);
+    expect(matches('^\\[[:alpha:]$', '[:')).toBe(true);
+    expect(matches('^\\[[:alpha:]$', '[b')).toBe(false);
     expect(matches('^\\[[:alpha:]$', '[:alpha:')).toBe(false);
   });
 

gitnexus/test/unit/scope-resolution/r/r-qualified-call.test.ts

@@ -369,6 +369,30 @@ describe('loadRPackageConfig: truncation only when a skipped subtree hides an un
       if (locked) await fs.chmod(locked, 0o755).catch(() => undefined);
     }
   });
+
+  it('an unreadable DESCRIPTION is truncated, so its qualifier stays unknown', async () => {
+    if (typeof process.getuid === 'function' && process.getuid() === 0) return; // root reads anything
+    let locked = '';
+    try {
+      const cfg = await withRepo(async (root) => {
+        locked = path.join(root, 'sub', 'DESCRIPTION');
+        await writePkg(path.join(root, 'sub'), 'hiddenpkg');
+        await fs.chmod(locked, 0o000);
+        // Guard: a platform that still reads a mode-000 file cannot exercise the catch.
+        await fs.readFile(locked).then(
+          () => {
+            throw new Error('DESCRIPTION is still readable; cannot simulate an I/O error');
+          },
+          () => undefined,
+        );
+      });
+      expect(cfg?.packages.has('hiddenpkg')).toBe(false);
+      expect(cfg?.truncated).toBe(true);
+      expect(rQualifierLocality('hiddenpkg', cfg as RPackageConfig, new Set())).toBe('unknown');
+    } finally {
+      if (locked) await fs.chmod(locked, 0o644).catch(() => undefined);
+    }
+  });
 });
 
 describe('hidesUndiscoveredPackage', () => {