fix(mcp): drop dead ESLint selector + suppress redundant grammar warning

Two minor PR #1383 review findings:

1. eslint.config.mjs: removed Selector 3 (`Property[key.name='write'].properties:has(...)`).
   `.properties` is not a valid attribute on a Property node in the ESTree
   AST, so the :has clause never matched — dead code. Selector 4 covers
   the canonical `const { write } = process.stdout` shape; tightened its
   comment to make that explicit.

2. cli/mcp.ts: removed the unconditional warnMissingOptionalGrammars call
   at MCP startup. The analyze path already emits this warning at index
   time with relevantExtensions filtered to the repo's actual file types,
   and a repo can only be served by MCP after analyze has run. Repeating
   the warning unconditionally on every MCP session was pure noise on
   machines whose indexed repos don't use .dart/.proto.

eslint.config.mjs

@@ -99,12 +99,11 @@ export default [
             'Direct process.stdout.write is forbidden in MCP-reachable code. Route diagnostics through console.error or process.stderr.write — the MCP stdio transport owns stdout for JSON-RPC frames.',
         },
         {
-          selector:
+          // Catches the canonical destructuring shape:
-            "VariableDeclarator > ObjectPattern > Property[key.name='write'].properties:has(MemberExpression[object.name='process'][property.name='stdout'])",
+          //   const { write } = process.stdout;
-          message:
+          // (and any other ObjectPattern destructure rooted at process.stdout)
-            'Destructuring write off process.stdout is forbidden in MCP-reachable code — bypasses the sentinel. Use process.stderr.write for diagnostics.',
+          // which would otherwise capture a reference to the original write
-        },
+          // and bypass the sentinel.
-        {
           selector:
             "VariableDeclarator[init.type='MemberExpression'][init.object.name='process'][init.property.name='stdout'] > ObjectPattern",
           message:

gitnexus/src/cli/mcp.ts

@@ -43,18 +43,18 @@ export const mcpCommand = async () => {
 
   // Now safe to dynamically import the heavy backend modules. Anything
   // they emit to stdout during evaluation will route through the sentinel.
-  const [{ startMCPServer }, { LocalBackend }, { warnMissingOptionalGrammars }] = await Promise.all(
+  const [{ startMCPServer }, { LocalBackend }] = await Promise.all([
-    [
+    import('../mcp/server.js'),
-      import('../mcp/server.js'),
+    import('../mcp/local/local-backend.js'),
-      import('../mcp/local/local-backend.js'),
+  ]);
-      import('./optional-grammars.js'),
-    ],
-  );
 
-  // Surface missing optional grammars at startup so users learn why
+  // Note: missing-optional-grammar warnings are emitted by `gitnexus analyze`
-  // .dart/.proto files won't be parsed instead of silently getting a
+  // (with `relevantExtensions` filtered to the repo's actual file types) at
-  // degraded index.
+  // index time. A repo can only be served by MCP after it has been analyzed,
-  warnMissingOptionalGrammars({ context: 'mcp' });
+  // so the user has already been warned through the path that knows whether
+  // the repo even contains .dart/.proto files. Repeating an unconditional
+  // warning at every MCP startup would be pure noise on machines whose
+  // indexed repos don't use those grammars.
 
   // Initialize multi-repo backend from registry.
   // The server starts even with 0 repos — tools call refreshRepos() lazily,