rota-decide — Capture Hard-Boundary Decisions

Distill an active commitment from the session into .rota/DECISIONS.md, by topic, so future work treats it as a hard constraint. Decisions are active (boundaries with forbids/permits); /rota-learn captures passive knowledge (gotchas, conventions).

Copy this checklist and track your progress:

- [ ] Step 1 — Mode (default vs source-prefill)
- [ ] Step 2 — Identify the Candidate Decision
- [ ] Step 3 — Compose the Four Parts
- [ ] Step 4 — Classify by Topic
- [ ] Step 5 — Confirmation Gate
- [ ] Step 6 — Merge into DECISIONS.md
- [ ] Step 7 — Update the Decisions Index
- [ ] Step 8 — Confirm