Expose MCP resource discovery controls to AI clients

[Widthdom]

Summary

• Teach MCP initialize.instructions how to use exact-path resource templates, filtered resources/list discovery, cursor continuation, and bounded resources/read calls.
• Publish the accepted resources/list extension parameters, bounds, generated-file default, and cursor semantics under result._meta.discovery_contract.
• Add regression coverage, bilingual user/developer documentation, and a bilingual changelog fragment.

Why

resources/list supports useful non-standard parameters (path, lang, includeGenerated, and maxBytes), but protocol methods do not expose a tool-style input schema. AI clients therefore had to guess that these controls existed even though the implementation and documentation already supported them.

This change makes the current resource-discovery contract discoverable in-band without changing existing request behavior.

Impact

AI clients can now choose exact-path reads or bounded repository browsing directly from the MCP handshake and response metadata. Pagination remains opaque and bound to both the index generation and the canonical filters.

Serializer audit

The separately reported trimmed-release tools/list failure involving missing System.String JsonTypeInfo metadata was already tracked as #178 and fixed by #1066. That fix is included in the v1.40.1 tag, and its existing serializer-fallback regression test passes in both target frameworks. No duplicate serializer change is included here.

Validation

• dotnet build CodeIndex.sln -c Release -p:UseSharedCompilation=false
• Full Debug test suite:
  • net8.0: 10,447 passed, 7 skipped, 0 failed
  • net9.0: 9,989 passed, 404 skipped, 0 failed
• Focused Release tests for initialize guidance, resource discovery metadata, and the MCP tools/list is silently dropped (no JSON-RPC error response) on the trimmed release binary — AI clients hang on the first handshake step #178 serializer fallback: 3 passed on both net8.0 and net9.0
• Live stdio JSON-RPC smoke for initialize and filtered resources/list
• dotnet run --project tools/CodeIndex.Changelog -- check
• Post-commit build and cdidx index . --commits HEAD; status --check reports index_matches_workspace: true