Propose Section

Workflow

Per qualifying cluster:
- [ ] Step 1: Name the cluster (working name from centroid codes)
- [ ] Step 2: Call write-section-promise for the one-sentence promise
- [ ] Step 3: Score each member post: tight | fair | borderline
- [ ] Step 4: Check non-overlap against existing section-map.md and other proposals this run
- [ ] Step 5: Assign fit_confidence:
    - high: ≥5 tight-fit posts + strong cohesion + unambiguous non-overlap
    - medium: 3-4 posts with mixed fit + narrowing promise
    - low: borderline throughout; defer
    - provisional: confident enough to name, uncertain enough to need probation
- [ ] Step 6: Write proposal block with reasons_to_reject (steelman the case against)

Output