feat: new MCP tools — get/list/update drawer, hook settings, export (resolves #635) (#667)

* feat: MCP reliability — inode detection, WAL rotation, metadata cache, search limits

Infrastructure hardening for the MCP server:
- Detect palace DB replacement via inode tracking (repair command support)
- WAL rotation to prevent unbounded WAL growth
- _fetch_all_metadata() + _get_cached_metadata() with 60s TTL for taxonomy/status
- _MAX_RESULTS cap (100) with limit clamping [1, _MAX_RESULTS]
- max_distance parameter for similarity threshold in search
- Handle all notifications/* methods, null arguments, method=None
- Remove duplicate _client_cache = None declarations
- searcher.py max_distance parameter passthrough

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: new MCP tools (get/list/update drawer, hook settings, memories filed), export, normalize

New MCP tools:
- mempalace_get_drawer: fetch single drawer by ID with full content
- mempalace_list_drawers: paginated listing with wing/room filter
- mempalace_update_drawer: update content/wing/room on existing drawers
- mempalace_hook_settings: get/set hook behavior (silent_save, desktop_toast)
- mempalace_memories_filed_away: check latest checkpoint status

Also includes:
- exporter.py: export palace as browsable markdown files
- normalize.py: tool_use/tool_result capture for richer transcript mining
- layers.py: updated for new tool integration
- config.py: hook settings properties (hook_silent_save, hook_desktop_toast)

Depends on PR 3 (reliability) for _MAX_RESULTS, _metadata_cache, WAL logging.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: normalize.py handles string messages and Read offset type mismatch

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: params null guard, L2→cosine docs, empty tool_use_map key guard

- Handle explicit null in MCP params (request.get("params") or {})
- Fix search tool description: L2 → cosine distance (collection uses hnsw:space=cosine)
- Guard against empty string key in tool_use_map from malformed JSONL entries

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: rename ambiguous var 'l' to 'line' (E741 lint)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: address code review findings (5 issues)

1. min_similarity backwards-compat: convert similarity to distance scale
   (1.0 - similarity) instead of passing raw value as max_distance
2. Restore structured error reporting (error + partial fields) in
   tool_status, tool_list_wings, tool_list_rooms, tool_get_taxonomy
   — reverts silent except:pass that dropped #647 security hardening
3. inode cache: remove falsy-zero short-circuit so missing DB file
   triggers reconnect instead of reusing stale client
4. _fetch_all_metadata: check for empty batch before extending/advancing
   offset to prevent infinite loop on concurrent deletion
5. KG initialization: only override path when --palace is explicit;
   default runs use KnowledgeGraph's built-in default path

Co-authored-by: jphein <jphein@users.noreply.github.com>

---------

Co-authored-by: jp <jp@jphein.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: jphein <jphein@users.noreply.github.com>

mempalace/config.py

@@ -173,6 +173,27 @@ class MempalaceConfig:
         """Mapping of hall names to keyword lists."""
         return self._file_config.get("hall_keywords", DEFAULT_HALL_KEYWORDS)
 
+    @property
+    def hook_silent_save(self):
+        """Whether the stop hook saves directly (True) or blocks for MCP calls (False)."""
+        return self._file_config.get("hooks", {}).get("silent_save", True)
+
+    @property
+    def hook_desktop_toast(self):
+        """Whether the stop hook shows a desktop notification via notify-send."""
+        return self._file_config.get("hooks", {}).get("desktop_toast", False)
+
+    def set_hook_setting(self, key: str, value: bool):
+        """Update a hook setting and write config to disk."""
+        if "hooks" not in self._file_config:
+            self._file_config["hooks"] = {}
+        self._file_config["hooks"][key] = value
+        try:
+            with open(self._config_file, "w", encoding="utf-8") as f:
+                json.dump(self._file_config, f, indent=2, ensure_ascii=False)
+        except OSError:
+            pass
+
     def init(self):
         """Create config directory and write default config.json if it doesn't exist."""
         self._config_dir.mkdir(parents=True, exist_ok=True)