Add Phase 4: Task Generation documentation and execution process

- Introduced comprehensive guidelines for generating implementation plan documents (IMPL_PLAN.md, task JSONs, TODO_LIST.md) using the action-planning-agent.
- Defined auto mode for user configuration with default settings.
- Outlined core philosophy emphasizing planning only, agent-driven document generation, and memory-first context loading.
- Detailed execution process divided into phases: User Configuration, Context Preparation, Single Agent Planning, N Parallel Planning, and Integration.
- Included lifecycle management for user configuration and agent interactions.
- Specified document generation lifecycle with clear expectations for outputs and quality standards.

Author: catlog22