/speckit.plan — create the implementation plan

Gate: the current feature must already have a completed spec.md — read it first; if it is missing or full of unresolved markers, stop and say so.

Run python3 speckit.py plan — it seeds plan.md next to the spec (the command refuses to run while spec.md is missing).
Fill plan.md from the spec: the concrete stack in ## Technical Context, the intended source layout in ## Structure, and each significant choice with rationale and rejected alternative in ## Decisions.
Check every decision against memory/constitution.md; justify or simplify anything that violates an article.
Run python3 speckit.py status to confirm the phase is recorded.