refactor: remove QMD semantic indexing — keep keyword search only

Remove the entire QMD search engine (semantic indexing, hybrid search,
vector embeddings) and replace with a simple walkdir-based keyword
search. QMD never worked reliably in production, added bundle bloat,
and showed "Index failed" in the status bar.

What changed:
- Rust: deleted indexing.rs, rewrote search.rs as pure keyword search
- Frontend: removed useIndexing hook, IndexingBadge, hybrid search
- Menu: removed "Reindex Vault" command from palette and menu bar
- Config: removed qmd from bundle resources and build script
- Deleted tools/qmd/ (QMD CLI tool, MCP server, tests)
- Updated docs (ARCHITECTURE, ABSTRACTIONS, GETTING-STARTED)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/hooks/useCommandRegistry.ts

@@ -25,7 +25,6 @@ interface CommandRegistryConfig {
   onInstallMcp?: () => void
   onEmptyTrash?: () => void
   trashedCount?: number
-  onReindexVault?: () => void
   onReloadVault?: () => void
   onRepairVault?: () => void
   onSetNoteIcon?: () => void
@@ -169,7 +168,6 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
     onRemoveActiveVault, onRestoreGettingStarted, isGettingStartedHidden, vaultCount,
     mcpStatus, onInstallMcp,
     onEmptyTrash, trashedCount,
-    onReindexVault,
     onReloadVault,
     onRepairVault,
     onSetNoteIcon,
@@ -256,7 +254,6 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
       { id: 'restore-getting-started', label: 'Restore Getting Started Vault', group: 'Settings', keywords: ['vault', 'restore', 'demo', 'getting started', 'reset'], enabled: !!isGettingStartedHidden && !!onRestoreGettingStarted, execute: () => onRestoreGettingStarted?.() },
       { id: 'check-updates', label: 'Check for Updates', group: 'Settings', keywords: ['update', 'version', 'upgrade', 'release'], enabled: true, execute: () => onCheckForUpdates?.() },
       { id: 'install-mcp', label: mcpStatus === 'installed' ? 'Restore MCP Server' : 'Install MCP Server', group: 'Settings', keywords: ['mcp', 'claude', 'ai', 'tools', 'install', 'restore', 'fix', 'repair'], enabled: true, execute: () => onInstallMcp?.() },
-      { id: 'reindex-vault', label: 'Reindex Vault', group: 'Settings', keywords: ['reindex', 'index', 'search', 'rebuild', 'refresh'], enabled: !!onReindexVault, execute: () => onReindexVault?.() },
       { id: 'reload-vault', label: 'Reload Vault', group: 'Settings', keywords: ['reload', 'refresh', 'rescan', 'sync', 'filesystem', 'cache'], enabled: !!onReloadVault, execute: () => onReloadVault?.() },
       { id: 'repair-vault', label: 'Repair Vault', group: 'Settings', keywords: ['repair', 'fix', 'restore', 'config', 'agents', 'themes', 'missing', 'reset', 'flatten', 'structure'], enabled: !!onRepairVault, execute: () => onRepairVault?.() },
 
@@ -282,7 +279,7 @@ export function useCommandRegistry(config: CommandRegistryConfig): CommandAction
     vaultTypes,
     onRemoveActiveVault, onRestoreGettingStarted, isGettingStartedHidden, vaultCount,
     mcpStatus, onInstallMcp, onEmptyTrash, trashedCount,
-    onReindexVault, onReloadVault, onRepairVault,
+    onReloadVault, onRepairVault,
     onSetNoteIcon, onRemoveNoteIcon, activeNoteHasIcon,
     isSectionGroup, noteListFilter, onSetNoteListFilter,
     onOpenInNewWindow,