Repair and promote smaller model profiles under strict gates

[tsotchke]

Goal
Improve the 386-min and 486DX2 model-profile queue without letting weak repairs into release artifacts.

Acceptance criteria

• Retrain candidates from the clean gold curriculum or a documented successor corpus.
• Failed candidates remain recorded as negative evidence and excluded from release payloads.
• Promotion requires strict host quality, DOS vector/perf evidence where applicable, and updated model inventory.
• Improvement backlog reflects the new decision state.

Evidence gate
python3 scripts/refresh_model_quality_reports.py
python3 scripts/plan_model_quality_repairs.py
python3 scripts/write_improvement_backlog.py
python3 scripts/audit_exported_models.py --strict
python3 scripts/build_preview_release.py --manifest-only

Boundary
No physical hardware validation is claimed by this issue.