feat(HAI-005): add auto-merge functionality for in-review tasks

- Add autoMerge boolean to Settings model with default false
- Add auto-merge toggle UI to the In Review column header
- Implement server-side auto-merge behavior in dashboard command
- Fix pre-existing build errors in types, executor, and dashboard server
- Update README with auto-merge documentation

packages/dashboard/app/components/Board.tsx

@@ -13,9 +13,11 @@ interface BoardProps {
   onCancelCreate: () => void;
   onCreateTask: (input: TaskCreateInput) => Promise<Task>;
   onNewTask: () => void;
+  autoMerge: boolean;
+  onToggleAutoMerge: () => void;
 }
 
-export function Board({ tasks, maxConcurrent, onMoveTask, onOpenDetail, addToast, isCreating, onCancelCreate, onCreateTask, onNewTask }: BoardProps) {
+export function Board({ tasks, maxConcurrent, onMoveTask, onOpenDetail, addToast, isCreating, onCancelCreate, onCreateTask, onNewTask, autoMerge, onToggleAutoMerge }: BoardProps) {
   return (
     <main className="board" id="board">
       {COLUMNS.map((col) => (
@@ -29,6 +31,7 @@ export function Board({ tasks, maxConcurrent, onMoveTask, onOpenDetail, addToast
           onOpenDetail={onOpenDetail}
           addToast={addToast}
           {...(col === "triage" ? { isCreating, onCancelCreate, onCreateTask, onNewTask } : {})}
+          {...(col === "in-review" ? { autoMerge, onToggleAutoMerge } : {})}
         />
       ))}
     </main>

packages/dashboard/app/components/Column.tsx

@@ -19,9 +19,11 @@ interface ColumnProps {
   onCancelCreate?: () => void;
   onCreateTask?: (input: TaskCreateInput) => Promise<Task>;
   onNewTask?: () => void;
+  autoMerge?: boolean;
+  onToggleAutoMerge?: () => void;
 }
 
-export function Column({ column, tasks, allTasks, maxConcurrent, onMoveTask, onOpenDetail, addToast, isCreating, onCancelCreate, onCreateTask, onNewTask }: ColumnProps) {
+export function Column({ column, tasks, allTasks, maxConcurrent, onMoveTask, onOpenDetail, addToast, isCreating, onCancelCreate, onCreateTask, onNewTask, autoMerge, onToggleAutoMerge }: ColumnProps) {
   const [dragOver, setDragOver] = useState(false);
 
   const handleDragOver = useCallback((e: React.DragEvent) => {
@@ -62,6 +64,17 @@ export function Column({ column, tasks, allTasks, maxConcurrent, onMoveTask, onO
         <div className={`column-dot dot-${column}`} />
         <h2>{COLUMN_LABELS[column]}</h2>
         <span className="column-count">{tasks.length}</span>
+        {column === "in-review" && onToggleAutoMerge && (
+          <label className="auto-merge-toggle" title={autoMerge ? "Auto-merge enabled" : "Auto-merge disabled"}>
+            <input
+              type="checkbox"
+              checked={!!autoMerge}
+              onChange={onToggleAutoMerge}
+            />
+            <span className="toggle-slider" />
+            <span className="toggle-label">Auto-merge</span>
+          </label>
+        )}
         {onNewTask && (
           <button className="btn btn-primary btn-sm" onClick={onNewTask}>
             + New Task

packages/dashboard/app/components/SettingsModal.tsx

@@ -9,7 +9,7 @@ interface SettingsModalProps {
 }
 
 export function SettingsModal({ onClose, addToast }: SettingsModalProps) {
-  const [form, setForm] = useState<Settings>({ maxConcurrent: 2, maxWorktrees: 4, pollIntervalMs: 15000, groupOverlappingFiles: false });
+  const [form, setForm] = useState<Settings>({ maxConcurrent: 2, maxWorktrees: 4, pollIntervalMs: 15000, groupOverlappingFiles: false, autoMerge: false });
   const [loading, setLoading] = useState(true);
 
   useEffect(() => {