feat(E): Unified Search — 24 Tasks complete

- SPIKE-E: FTS+Vector+Permission benchmark on 10k records (all <30ms)
- E-PROV: supports_fts/vector/rag/graph capability flags on all providers
- E-FTS/VEC: All 11 providers refactored to BaseSearchProvider with permission filtering
- E-PERM: Over-fetch strategy for vector+permission (15x faster than ANY() filter)
- E-FUSE: rrf_fusion_multi() for N-way RRF over FTS+Vector+RAG+Graph
- E-LLM: Query understanding cleaned up to use central llm_complete()
- E-CHUNK: Document chunking module + document_chunks table with HNSW index
- E-EMB: Chunk embedding ARQ jobs (index_file_chunks, reindex_chunks)
- E-RAG: RAG retrieval via FileSearchProvider.search_rag()
- E-GRAPH: GraphRAG BFS traversal via GraphRAGSearchProvider.search_graph()
- E-IX-EVT: Auto-indexing via outbox events + delete/cleanup handlers
- E-IX-RE: Batch reindex with progress tracking + reindex_all job
- E-DATA-LIFE: Lifecycle module (remove/rebuild/restore/correct) + API endpoints
- E-K-MEM: AgentMemorySearchProvider
- E-P-AI: AIChatSearchProvider
- E-P-WF: WorkflowSearchProvider
- E-P-COMM: ConversationSearchProvider verified (already on BaseSearchProvider)
- E-API: Filter params (date_from/to, tags, sort) + /facets endpoint
- E-TOOL: unified_search AI tool registered in ToolRegistry
- E-MCP: Search tool in MCP server with normal RBAC/tenant checks
- E-UI-CMD: CommandPalette (Cmd+K) with debounced search + recent searches
- E-UI-FAC: SearchFacets, SearchResultCard, SavedSearches components
- E-TEST: 40 new tests in test_unified_search_phase_e.py (105 total green)
- E-DOC: api-documentation.md, plugin-development-guide.md, test-strategy.md updated

105 tests passing, TypeScript clean.

frontend/src/hooks/useCommandPalette.ts

@@ -0,0 +1,37 @@
+import { useEffect } from 'react';
+import { useCommandPaletteStore } from '@/store/commandPaletteStore';
+
+/**
+ * useCommandPalette — global command palette (Cmd+K / Ctrl+K) state.
+ *
+ * Backed by a shared Zustand store so the TopBar button and the
+ * CommandPalette component stay in sync. Registers the global keyboard
+ * shortcut listener once; typing inside inputs/textareas/contenteditable
+ * is not hijacked.
+ */
+export function useCommandPalette() {
+  const isOpen = useCommandPaletteStore((s) => s.isOpen);
+  const open = useCommandPaletteStore((s) => s.open);
+  const close = useCommandPaletteStore((s) => s.close);
+  const toggle = useCommandPaletteStore((s) => s.toggle);
+
+  useEffect(() => {
+    const handleKeyDown = (e: KeyboardEvent) => {
+      const isModifier = e.metaKey || e.ctrlKey;
+      if (!isModifier || e.key.toLowerCase() !== 'k') return;
+
+      // Don't hijack typing inside editable fields
+      const target = e.target as HTMLElement | null;
+      const tag = target?.tagName?.toLowerCase();
+      if (tag === 'input' || tag === 'textarea' || target?.isContentEditable) return;
+
+      e.preventDefault();
+      useCommandPaletteStore.getState().toggle();
+    };
+
+    document.addEventListener('keydown', handleKeyDown);
+    return () => document.removeEventListener('keydown', handleKeyDown);
+  }, []);
+
+  return { isOpen, open, close, toggle };
+}