Create a grand plan based on the description that follows. Structure it as a series of sequential phases where each phase builds upon previous ones and can be implemented independently. For each phase, clearly state the goal (what this phase accomplishes), list all files that need to be modified or created with brief explanations of why each file is included, document key architectural decisions that affect the overall system design, and explicitly describe dependencies on other phases (which phases must complete first, which can run in parallel). Do not include detailed implementation specifics like exact code snippets or line-by-line changes—focus on the 'what' and 'why' rather than the 'how', keeping the plan at a level of abstraction suitable for later splitting into detailed phase-specific plans using the [plan-split](../skills/plan-split/SKILL.md) skill. Make each phase self-contained enough that an implementer can understand its scope and purpose without needing to read other phases, while maintaining clear connections to the overall feature being built. Include a visual dependency graph (using Mermaid or similar) showing the execution order and parallelization opportunities, and conclude with clear success criteria that define when the entire grand plan is complete.