feat(KB-648): enable parallel test execution and optimize test performance

- Optimize backup tests using fake timers instead of real timeouts

- Enable parallel file execution in core, engine, CLI, and dashboard packages

- Add inline test helpers to reduce dependencies in dashboard routes tests

- Update executor tests with exact command matching and improved assertions

- Update AGENTS.md with test optimization patterns (fake timers, unique temp dirs)

packages/dashboard/app/components/WorktreeGroup.tsx

@@ -15,7 +15,7 @@ interface WorktreeGroupProps {
     id: string,
     updates: { title?: string; description?: string; dependencies?: string[] }
   ) => Promise<Task>;
-  onOpenFilesForTask?: (taskId: string, worktree: string | undefined, column: string) => void;
+  onOpenFilesForTask?: (taskId: string) => void;
 }
 
 function WorktreeGroupComponent({