Plan the challenge

Read the challenge spec and inspect the project enough to make its tasks fit the existing stack and codebase. Make reasonable assumptions and record them in PLAN.md; never ask clarifying questions.

Write PLAN.md with:

• MUST-HAVE: at most 10 checkbox tasks, ordered by build dependency and implementation sequence.
• NICE-TO-HAVE: at most 5 checkbox tasks, ordered by value.
• Assumptions: concise decisions made where the spec was silent or ambiguous.

Stop after writing the plan. Do not implement tasks.

If PLAN.md already exists, do not overwrite it. Tell the user to use the add skill instead.