refactor: extract hooks from App.tsx to improve code health (#62)

Extract vault management (useVaultSwitcher), git history loading
(useGitHistory), dialog state (useDialogs), and keyboard/command
setup (useAppCommands) into dedicated hooks. App.tsx code health
improves from 8.95 to 10.0 — all extracted hooks also score 10.0.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/hooks/useDialogs.ts

@@ -3,25 +3,29 @@ import { useState, useCallback } from 'react'
 export function useDialogs() {
   const [showCreateTypeDialog, setShowCreateTypeDialog] = useState(false)
   const [showQuickOpen, setShowQuickOpen] = useState(false)
-  const [showCommitDialog, setShowCommitDialog] = useState(false)
+  const [showCommandPalette, setShowCommandPalette] = useState(false)
   const [showAIChat, setShowAIChat] = useState(false)
   const [showSettings, setShowSettings] = useState(false)
+  const [showGitHubVault, setShowGitHubVault] = useState(false)
 
   const openCreateType = useCallback(() => setShowCreateTypeDialog(true), [])
   const closeCreateType = useCallback(() => setShowCreateTypeDialog(false), [])
   const openQuickOpen = useCallback(() => setShowQuickOpen(true), [])
   const closeQuickOpen = useCallback(() => setShowQuickOpen(false), [])
-  const openCommitDialog = useCallback(() => setShowCommitDialog(true), [])
-  const closeCommitDialog = useCallback(() => setShowCommitDialog(false), [])
+  const openCommandPalette = useCallback(() => setShowCommandPalette(true), [])
+  const closeCommandPalette = useCallback(() => setShowCommandPalette(false), [])
   const openSettings = useCallback(() => setShowSettings(true), [])
   const closeSettings = useCallback(() => setShowSettings(false), [])
+  const openGitHubVault = useCallback(() => setShowGitHubVault(true), [])
+  const closeGitHubVault = useCallback(() => setShowGitHubVault(false), [])
   const toggleAIChat = useCallback(() => setShowAIChat((c) => !c), [])
 
   return {
     showCreateTypeDialog, openCreateType, closeCreateType,
     showQuickOpen, openQuickOpen, closeQuickOpen,
-    showCommitDialog, openCommitDialog, closeCommitDialog,
+    showCommandPalette, openCommandPalette, closeCommandPalette,
     showAIChat, toggleAIChat,
     showSettings, openSettings, closeSettings,
+    showGitHubVault, openGitHubVault, closeGitHubVault,
   }
 }