build — implement spec

Single-thread native plan→execute. You are main Claude. No swarm.

LOAD

1. Read SPEC.md. If missing → tell user to invoke the spec skill first. Stop.
2. Read FORMAT.md once if not loaded (repo root; fallback ~/.claude/skills/spec/FORMAT.md).
3. Parse invocation args:
   • §T.n → that task only
   • --next → lowest-numbered row with status . or ~
   • --all or empty → every . row in §T order

PLAN

Native plan mode. For chosen task(s):