CLI-33: Implement prompt queue feature

[szmania]

CLI-33: Implement Prompt Queue Feature

Purpose

This PR implements the prompt queue feature requested in CLI-33. It enables users to queue prompts for processing after current tasks complete, providing better control over workflow execution in the CLI.

Design Considerations

Architecture

• In-Memory FIFO Queue: The prompt queue is stored as an in-memory list on the Commands class instance, ensuring it persists across command executions within a single session but is cleared on session restart
• Thread Safety: Uses asyncio.Lock for atomic queue operations to prevent race conditions in the async event loop
• Management Command Guard: Queue processing is explicitly excluded for /queue, /list-queue, and /remove-queue commands to prevent infinite recursion and ensure management commands can be executed during active prompt processing

Queue Processing

• Integrated into Commands.execute() finally block, after cmd_running_event is set
• Sequential FIFO processing ensures queued prompts execute in order after current command completes
• Self-triggering guard via _processing_queue flag prevents infinite loops from queued prompts that queue additional items
• Exception resilience: Generic exceptions during queued prompt execution are logged but don't halt subsequent queue processing
• Signal propagation: SwitchCoderSignal and ReloadProgramSignal are re-raised to maintain proper control flow

Constraints

• Maximum queue size: 100 items (prevents memory exhaustion)
• Maximum prompt length: 10,000 characters per queued item
• Session-specific: Queue state is lost on CLI restart (by design)

What Changed

New Files

1. cecli/commands/queue.py - QueueCommand class implementing /queue <prompt> to add prompts to the queue
2. cecli/commands/list_queue.py - ListQueueCommand class implementing /list-queue to display queued items
3. cecli/commands/remove_queue.py - RemoveQueueCommand class implementing /remove-queue [index|*] for interactive or direct removal
4. cecli/tests/test_queue_commands.py - Comprehensive test suite with unit, integration, and E2E tests

Modified Files

1. cecli/commands/core.py:

   • Added prompt_queue, _queue_counter, _queue_lock, _processing_queue, _MANAGEMENT_COMMANDS state
   • Implemented queue management methods: _enqueue_prompt(), _dequeue_prompt(), _get_queue_length(), _remove_from_queue(), _clear_queue(), _process_queued_prompts()
   • Modified execute() to trigger queue processing after management command check
   • Fixed run() to handle all / prefixed commands properly
   • Modified execute() to skip clearing cmd_running_event for management commands

2. cecli/commands/__init__.py:

   • Registered QueueCommand, ListQueueCommand, and RemoveQueueCommand in CommandRegistry
   • Added all three command classes to __all__ list

3. README.md:

   • Added "Prompt Queue Management" section documenting all three new commands
   • Included usage syntax, examples, and constraints
   • Explained queue processing lifecycle and limits

Testing

All tests pass successfully:

• Unit tests for queue data structure operations (enqueue, dequeue, remove, clear, etc.)
• Integration tests for command registration and execution
• E2E tests for full queue lifecycle and management during active commands
• Regression tests confirming existing commands remain functional
• Edge cases: empty queue, invalid indices, max size, long prompts

Related Issue

• Jira: CLI-33
• GitHub Project: cecli-dev