feat(issue): implement JSONL task generation and management for issue resolution

- Added `/issue:plan` command to generate a structured task plan from GitHub issues or descriptions, including delivery and pause criteria, and a dependency graph.
- Introduced JSONL schema for task entries to enforce structure and validation.
- Developed comprehensive issue command with functionalities for initializing, listing, adding, updating, and exporting tasks.
- Implemented error handling and user feedback for various operations within the issue management workflow.
- Enhanced task management with priority levels, phase results, and executor preferences.

Author: catlog22