feat(HAI-002): add maxWorktrees setting to limit total git worktrees

- Add maxWorktrees field to Settings interface with default of 4
- Enforce worktree limit in Scheduler.schedule() alongside maxConcurrent
- Wire setting through dashboard startup from persisted settings
- Include maxWorktrees in /api/config response
- Add Max Worktrees input to Settings Modal UI
- Backward compatible: existing configs without maxWorktrees use default

packages/cli/src/commands/dashboard.ts

@@ -49,8 +49,11 @@ export async function runDashboard(port: number, opts: { engine?: boolean; open?
       onError: (t, e) => console.log(`[engine] ✗ ${t.id}: ${e.message}`),
     });
 
+    const settings = await store.getSettings();
+
     const scheduler = new Scheduler(store, {
-      maxConcurrent: 2,
+      maxConcurrent: settings.maxConcurrent,
+      maxWorktrees: settings.maxWorktrees,
       onSchedule: (t) => console.log(`[engine] Scheduled ${t.id}`),
       onBlocked: (t, deps) => console.log(`[engine] ${t.id} blocked by ${deps.join(", ")}`),
     });