refactor: decompose KanbanBoard God Component into focused hooks (#147)

* refactor: seal useRepositorySearch API — replace raw setters with semantic actions (#143)

- Replace setSearchQuery with updateSearch
- Replace setSelectedRepos([]) with clearSelection
- Replace setIsAdding(true/false) with startAdding/finishAdding
- Replace setAddError with setAddingError/clearError
- All actions wrapped in useCallback for referential stability
- startAdding() combines setIsAdding(true) + clearError() atomically

* refactor: extract useKanbanDnD hook from KanbanBoard (#141, #145)

- Extract ~195 lines of DnD logic into src/hooks/board/useKanbanDnD.ts
- Move forgivingCollisionDetection, sensors, drag handlers, grid calculations
- Column sub-handlers (handleNewRowDrop, handleColumnInsertDrop, handleColumnSwap) included
- handleDragEnd split into column/card branches per #145
- History state stays in KanbanBoard via pushCardHistory/pushColumnHistory callbacks
- All handlers wrapped in useCallback with correct dependency arrays

* refactor: extract useKanbanUndo hook from KanbanBoard (#142)

- Extract history/columnHistory state, handleUndo, Z-key useEffect
- Hook is self-contained: keyboard shortcut registered internally
- Returns pushCardHistory/pushColumnHistory for useKanbanDnD consumption
- KanbanBoard no longer imports setStatusLists/setRepoCards directly
- Removes ~73 lines from KanbanBoard

* refactor: extract useCommentState hook from KanbanBoard (#144)

- Extract comments state + 3 CRUD handlers into useCommentState hook
- Preserve optimistic updates, Sentry error tracking, and toast feedback
- KanbanBoard now imports zero direct server actions
- Removed unused imports: useState, useCallback, Sentry, toast, CommentColor
- KanbanBoard reduced from 825 → 295 lines (completes decomposition)

* fix: address CodeRabbit review — error handling + Z-key modifier guard

- useCommentState: convert unreachable try/catch to result.success pattern
  (server actions return ActionResult, never throw)
- useCommentState: add rollback + toast on all 3 handlers failure path
- useCommentState: remove duplicate Sentry reporting (server already reports)
- useKanbanUndo: guard Z-key handler with !ctrlKey && !metaKey && !altKey
  to avoid conflict with browser Ctrl+Z undo

* refactor: replace dynamic import with static for updateStatusListPosition

Address CodeRabbit nitpick: align updateStatusListPosition import
with other board actions that are already statically imported.

Author: ryota-murakami

src/components/Board/AddRepositoryCombobox.tsx

@@ -106,16 +106,17 @@ export const AddRepositoryCombobox = memo(function AddRepositoryCombobox({
   // --- Extracted hooks ---
   const {
     searchQuery,
-    setSearchQuery,
+    updateSearch,
     deferredSearchQuery,
     selectedRepos,
-    setSelectedRepos,
     isAdding,
-    setIsAdding,
+    startAdding,
+    finishAdding,
     addError,
-    setAddError,
+    setAddingError,
     toggleRepoSelection,
     removeSelectedRepo,
+    clearSelection,
   } = useRepositorySearch()
 
   const { currentUser, filteredOrganizations, isLoadingOrgs, organizations } =
@@ -253,8 +254,7 @@ export const AddRepositoryCombobox = memo(function AddRepositoryCombobox({
     if (selectedRepos.length === 0) return
 
     try {
-      setIsAdding(true)
-      setAddError(null)
+      startAdding()
 
       // Server Action: Add repositories to board with duplicate detection
       const result = await addRepositoriesToBoard(
@@ -264,7 +264,9 @@ export const AddRepositoryCombobox = memo(function AddRepositoryCombobox({
       )
 
       if (!result.success) {
-        setAddError(result.errors?.join(', ') || 'Failed to add repositories')
+        setAddingError(
+          result.errors?.join(', ') || 'Failed to add repositories',
+        )
         return
       }
 
@@ -287,8 +289,8 @@ export const AddRepositoryCombobox = memo(function AddRepositoryCombobox({
       )
 
       // Success: clear selection and close combobox
-      setSelectedRepos([])
-      setSearchQuery('')
+      clearSelection()
+      updateSearch('')
       // Close combobox (supports both controlled and uncontrolled modes)
       if (onOpenChange) {
         onOpenChange(false)
@@ -304,11 +306,11 @@ export const AddRepositoryCombobox = memo(function AddRepositoryCombobox({
         onQuickNoteFocus()
       }, 100)
     } catch (err) {
-      setAddError(
+      setAddingError(
         err instanceof Error ? err.message : 'Error adding repositories',
       )
     } finally {
-      setIsAdding(false)
+      finishAdding()
     }
   }
 
@@ -367,7 +369,7 @@ export const AddRepositoryCombobox = memo(function AddRepositoryCombobox({
             ref={searchInputRef}
             type="text"
             value={searchQuery}
-            onChange={(e) => setSearchQuery(e.target.value)}
+            onChange={(e) => updateSearch(e.target.value)}
             placeholder="Search repositories..."
             className="border-input bg-background text-foreground focus:border-primary focus:ring-primary w-full rounded-md border px-3 py-2 text-sm focus:ring-1 focus:outline-none"
             aria-label="Search repositories"