feat(mcp): drop GraphRAG ask from the registered MCP tool surface

Benchmarking showed the MCP ask tool failing on every call (the spawned server
env carries only FalkorDB coordinates, no LLM key) and, when keyed, returning
File-level fuzzy matches rather than the structural answers the nav workflow
needs — an LLM round-trip per call for no signal. Expose only the deterministic
structural tools; GraphRAG ask stays on the HTTP /api/chat path. #681's ask
implementation is left intact (re-enable by re-adding the import).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: DvirDukhan

api/mcp/tools/__init__.py

@@ -4,4 +4,11 @@
 ``api.mcp.server``. Import this package to register all tools.
 """
 
+# NOTE: the GraphRAG-backed ``ask`` tool is intentionally NOT part of the MCP
+# surface. In benchmarking it failed on every call ("Missing GOOGLE_API_KEY/
+# GEMINI_API_KEY") because the spawned MCP server env carries only FalkorDB
+# coordinates, and even when keyed it returned File-level fuzzy matches rather
+# than the structural answers the nav workflow needs. Burning an LLM round-trip
+# per call for no signal, so we expose only the deterministic structural tools.
+# GraphRAG ask remains available on the HTTP /api/chat path.
 from . import structural  # noqa: F401  (registers tools on import)