feat: implement local indexer for project-knowledge and add memory hybrid search functionality

scripts/mcp/aiw-context-mcp/README.md

@@ -42,10 +42,19 @@ python3 scripts/mcp/aiw-context-mcp/server.py --transport stdio
 - `communication_thread_context`
 - `project_current_context`
 - `project_search_memory`
+- `memory_hybrid_search`
 - `photos_latest`
 
 All tools are read-only. Mattermost tools read `ai/inbox/mattermost-mirror/`; photo tools list local Photo Inbox files without embedding image data; project tools read canonical Markdown under `project-knowledge/`.
 
+`memory_hybrid_search` reads the derived local index built by:
+
+```bash
+python3 scripts/aiw/indexer.py build --profile fidelity
+```
+
+If the index is missing, it falls back to bounded live Markdown search over `project-knowledge/`. The index is not canonical memory; `project-knowledge/` remains the source of truth.
+
 Mattermost latest/date/standup tools filter to the active profile's context channels by default. For Fidelity, that list lives in `profiles/fidelity/context-sources.json`. Pass explicit `channels` to override the profile list, or `include_all_channels: true` when broad unfiltered mirror evidence is intentionally needed.
 
 ## Resources