feat: add local agent MCP tools and optional source-grounded AI answers

docs/ROADMAP.md

@@ -64,6 +64,22 @@ Status: implementation started; no production release yet. Windows VM tests use
 - [ ] Execute Linux/macOS platform tests; create Windows/macOS/Linux installers.
 - [ ] Signing/notarization configuration, upgrade/rollback validation, release instructions.
 
+## 6. Local agents and optional answers
+
+- [x] Read-only MCP stdio server using the shared search service, persistent
+  Google worker, structured filters, source citations and measured search stats.
+- [x] End-to-end MCP initialization, discovery, search, invalid-input and
+  source-access tests; no protocol text mixed with diagnostic stdout.
+- [x] Installable agent skill and copyable MCP client configuration, with clear
+  database scope, readiness and untrusted-source handling.
+- [x] Optional OpenAI-compatible summaries/questions, disabled by default;
+  explicit selected-source action, endpoint disclosure, bounded payloads,
+  credentials kept out of persistent settings, diagnostics and error messages.
+- [x] Verify real HTTP wire format against a local test endpoint; reject invalid
+  settings, stale sources and unauthorized citations; preserve search on failure.
+- [ ] Native UI interaction and chosen-provider quality/latency checks before
+  claiming production-ready answers or compatibility with every provider.
+
 Completion requires recorded evidence; targets are not measured results.
 
 ## Completed foundation details