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/layers.py

@@ -23,6 +23,7 @@ from collections import defaultdict
 
 from .config import MempalaceConfig
 from .palace import get_collection as _get_collection
+from .searcher import build_where_filter
 
 
 # ---------------------------------------------------------------------------
@@ -81,6 +82,7 @@ class Layer1:
 
     MAX_DRAWERS = 15  # at most 15 moments in wake-up
     MAX_CHARS = 3200  # hard cap on total L1 text (~800 tokens)
+    MAX_SCAN = 2000   # don't scan more than this for L1 generation
 
     def __init__(self, palace_path: str = None, wing: str = None):
         cfg = MempalaceConfig()
@@ -113,7 +115,7 @@ class Layer1:
             docs.extend(batch_docs)
             metas.extend(batch_metas)
             offset += len(batch_docs)
-            if len(batch_docs) < _BATCH:
+            if len(batch_docs) < _BATCH or len(docs) >= self.MAX_SCAN:
                 break
 
         if not docs:
@@ -198,13 +200,7 @@ class Layer2:
         except Exception:
             return "No palace found."
 
-        where = {}
-        if wing and room:
-            where = {"$and": [{"wing": wing}, {"room": room}]}
-        elif wing:
-            where = {"wing": wing}
-        elif room:
-            where = {"room": room}
+        where = build_where_filter(wing, room)
 
         kwargs = {"include": ["documents", "metadatas"], "limit": n_results}
         if where:
@@ -261,13 +257,7 @@ class Layer3:
         except Exception:
             return "No palace found."
 
-        where = {}
-        if wing and room:
-            where = {"$and": [{"wing": wing}, {"room": room}]}
-        elif wing:
-            where = {"wing": wing}
-        elif room:
-            where = {"room": room}
+        where = build_where_filter(wing, room)
 
         kwargs = {
             "query_texts": [query],
@@ -316,13 +306,7 @@ class Layer3:
         except Exception:
             return []
 
-        where = {}
-        if wing and room:
-            where = {"$and": [{"wing": wing}, {"room": room}]}
-        elif wing:
-            where = {"wing": wing}
-        elif room:
-            where = {"room": room}
+        where = build_where_filter(wing, room)
 
         kwargs = {
             "query_texts": [query],