Phase 2C.1: add reproducible teacher image quality benchmark

[xueyang-dev]

Summary

Phase 2C.1 adds a reproducible, teacher-reviewable quality benchmark for the fixed Phase 2C SD 1.5 teaching-image path.

• Defines 25 fixed-seed cases across all ten required teaching categories.
• Adds strict schema and identity binding for the fixed Model Package, Workflow Pack, Runtime, and prompt profile.
• Adds an interruptible, resumable, idempotent batch executor that uses only the controlled TeachingImageRequest entry point.
• Verifies PNG technical integrity, SHA-256, provenance, request identity, fixed negative prompt, and Asset Manifest registration.
• Adds a portable offline teacher review package with blank pending_review records and structured failure labels; no teacher scores are generated automatically.
• Documents pilot and full real-run evidence without committing images, Runtime, model, cache, or reports.

Real-run evidence

• Pilot: 3/3 real technical successes after using a persistent Runtime owner session; 3 review records pending.
• Full run: 25/25 real technical successes, 0 technical failures, 0 pending/invalidated, one fixed seed per case.
• Asset Manifest: 25 entries, all pending_review.
• Teacher review: 25 pending records, 0 imported/reviewed; no teaching-quality conclusions are claimed.
• An initial one-off Runtime starter produced a fail-closed ComfyUI BrokenPipeError; this was recorded and recovered by keeping the Runtime owner session alive. History/provenance checks were not weakened.

Validation

• npm test: 654 API tests passed, 3 skipped; Vite build passed; Web state contract passed.
• npm run test:e2e: 14 passed.
• git diff --check: passed.
• Focused benchmark/Ruff checks passed.
• macOS arm64 opt-in Runtime/model lifecycle and real generation were exercised locally.

Scope boundaries

This PR does not tune prompts, replace the model, modify the fixed Workflow Pack, add LoRA/ControlNet/custom nodes/multi-model support, fabricate teacher ratings, add cloud fallback, or merge automatically. It remains Draft pending real teacher review.