fix: inject SessionDB into AIAgent for WebUI sessions — enables session_search (#356)

* fix: inject SessionDB into AIAgent for WebUI sessions

session_search tool requires a SessionDB instance passed via the
session_db parameter. The CLI and gateway paths already do this,
but the WebUI streaming path was missing it, causing every
session_search call to return 'Session database not available'.

Initialize SessionDB before creating the AIAgent and pass it through.
Failure is non-fatal — a warning is printed and session_search
gracefully degrades.

* fix: inject SessionDB into AIAgent for WebUI sessions (enables session_search) (#356)

- api/streaming.py: initialize SessionDB() before AIAgent construction and
  pass session_db= kwarg so session_search works in WebUI sessions
- tests/test_sprint42.py: 7 new tests covering SessionDB injection, try/except
  guard, WARNING log, ordering, and AST lock-safety check
- CHANGELOG.md: v0.50.13 entry; 822 tests total (up from 815)

---------

Co-authored-by: 王昌旭 <wangchangxu@xiaohongshu.com>
Co-authored-by: Nathan Esquenazi <nesquena@gmail.com>

api/streaming.py

@@ -186,6 +186,14 @@ def _run_agent_streaming(session_id, msg_text, model, workspace, stream_id, atta
             _AIAgent = _get_ai_agent()
             if _AIAgent is None:
                 raise ImportError("AIAgent not available -- check that hermes-agent is on sys.path")
+
+            # Initialize SessionDB so session_search works in WebUI sessions
+            _session_db = None
+            try:
+                from hermes_state import SessionDB
+                _session_db = SessionDB()
+            except Exception as _db_err:
+                print(f"[webui] WARNING: SessionDB init failed — session_search will be unavailable: {_db_err}", flush=True)
             resolved_model, resolved_provider, resolved_base_url = resolve_model_provider(model)
 
             # Resolve API key via Hermes runtime provider (matches gateway behaviour).
@@ -235,6 +243,7 @@ def _run_agent_streaming(session_id, msg_text, model, workspace, stream_id, atta
                 enabled_toolsets=_toolsets,
                 fallback_model=_fallback_resolved,
                 session_id=session_id,
+                session_db=_session_db,
                 stream_delta_callback=on_token,
                 tool_progress_callback=on_tool,
             )