fix(agent): fall back to keyword tool selection when retrieval times out

The retrieval-timeout branch hard-coded ALWAYS_AVAILABLE, silently skipping
the deterministic keyword hints whenever the embedding backend was slow
(e.g. a remote endpoint cold-loading its model). Queries that named email
or calendar outright lost those tools and the model concluded the
integrations did not exist. Let the timeout fall through to the existing
keyword fallback instead — same baseline, plus the hints.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/agent_loop.py

@@ -2532,11 +2532,17 @@ async def stream_agent_loop(
                         )
                         logger.info(f"[tool-rag] Retrieved tools for query: {sorted(_relevant_tools - ALWAYS_AVAILABLE)}")
                     except asyncio.TimeoutError:
+                        # Leave _relevant_tools unset so the keyword fallback
+                        # below still runs. Hard-coding ALWAYS_AVAILABLE here
+                        # skipped the deterministic keyword hints whenever the
+                        # embedding backend was slow (e.g. a remote endpoint
+                        # cold-loading its model), silently stripping email/
+                        # calendar tools from queries that named them outright.
                         logger.warning(
-                            "[tool-rag] Retrieval exceeded %.1fs; falling back to always-available tools",
+                            "[tool-rag] Retrieval exceeded %.1fs; falling back to keyword tool selection",
                             _TOOL_SELECTION_TIMEOUT_SECONDS,
                         )
-                        _relevant_tools = set(ALWAYS_AVAILABLE)
+                        _relevant_tools = None
         except Exception as e:
             logger.warning(f"[tool-rag] Retrieval failed, using keyword fallback: {e}")
             _relevant_tools = None