Cervical Fluid Model — Remaining Refinement

[perki]

Remaining cervical-fluid model audit items from Plan 14: deep verification of ChartNeo 5-axis sub-peaks, UNC 9-combination consistency, Descriptive 49-option dimension mappings, plus per-method per-dimension confidence (observed: boolean) flags and a MODEL-DESIGN.md doc. Remaining items from Plan 14 (challenge/audit).

Plan source: _plans/XXX-Backlog/MODEL-MUCUS-REFINEMENT.md (private workspace)
Status (workspace): later → Project Status: Backlog

_{Tracked from the linked _plans/ directory above (see its ## Project tracking section). Phase narrative goes in this issue's comments — the body stays the high-level abstract.}