feat(robomp): added local issue indexing and commit-search tool support

- Added `ROBOMP_ISSUE_INDEX_SYNC_SECONDS` configuration and lifecycle-managed issue indexing through startup/shutdown hooks.
- Added issue/PR index tables with FTS5 triggers plus upsert and keyword/filter search helpers for indexed records.
- Added GitHub backend/proxy support for `IssueIndexEntry` and issue-index page retrieval, including webhook ingestion and periodic watermark-driven sync.
- Updated `gh_search_issues` to prefer local index queries when synchronized and added `search_commits` host tool with query modes and validation.

python/robomp/src/proxy/server.py

@@ -523,6 +523,22 @@ def create_proxy_app(settings: Settings) -> FastAPI:
             return _gh_error_response(exc)
         return JSONResponse({"items": [_serialize(s) for s in items]})
 
+    @app.get("/gh/v1/issue_index_entries")
+    async def list_issue_index_entries(
+        request: Request,
+        repo: str,
+        since: str | None = None,
+        page: int = 1,
+        per_page: int = 100,
+    ) -> JSONResponse:
+        await _authenticate(request)
+        github: GitHubClient = request.app.state.github
+        try:
+            items = await github.list_issue_index_entries(repo, since=since, page=page, per_page=per_page)
+        except GitHubError as exc:
+            return _gh_error_response(exc)
+        return JSONResponse({"items": [_serialize(s) for s in items]})
+
     @app.get("/gh/v1/comments")
     async def list_comments(request: Request, repo: str, number: int) -> JSONResponse:
         await _authenticate(request)