feat(task-queue): add task queue system for orchestrating Claude prompts

[StanGirard]

Summary

Implements a global task queue system for orchestrating multiple Claude prompts with:

• Three execution modes: print (-p background), interactive, and trust (--dangerously-skip-permissions)
• Sequential dependencies: Task chains (1 → 2 → 3) where each task waits for the previous one
• Session isolation: Each task creates its own tmux session
• Failure handling: Retry/Skip/Stop options when a task fails

Backend Changes

• SQLite migration v7 with tasks and task_templates tables
• tasks.ts database module with CRUD operations, batch creation, dependency management
• TaskQueueExecutor service that polls for ready tasks and executes them
• REST API endpoints: /api/tasks, /api/tasks/batch, /api/tasks/:id/retry, /api/tasks/:id/skip, etc.
• WebSocket events for real-time task updates (task-created, task-started, task-completed, task-failed)

Frontend Changes

• TaskQueuePanel: Linear-style compact UI in the sidebar with progress bar
• TaskCard: Sortable cards with drag-and-drop (@dnd-kit) for reordering
• TaskCreator: Modal for single task or batch (task chain) creation
• FailureDialog: Dialog for retry/skip/stop decisions on failed tasks
• useTaskQueue: Hook for state management and WebSocket integration

Design Inspiration

• Linear - Compact row design with status icons
• Vibe Kanban - Drag-and-drop patterns

Test plan

• All existing tests pass (359 tests)
• Build succeeds
• Manual: Create single task and verify execution
• Manual: Create task chain (3 tasks) and verify sequential execution
• Manual: Force a task failure and test Retry/Skip/Stop buttons
• Manual: Test drag-and-drop reordering
• Manual: Test all 3 execution modes

🤖 Generated with Claude Code