feat(trigger): complete v1.2 training console

[mshegolev]

Summary

• complete Phase 9 review/relabel workflow with filtered sample listing, category moves, review queue, and session-aware sanitized reports
• complete Phase 10 readiness gate with holdout evaluation, model-fingerprinted live-assist enable/status, and guarded auto-mode downgrade behavior
• update PRD, Quick Start, and GSD planning artifacts for v1.2 completion

Verification

• .venv/bin/python -m pytest -q tests/analysis/test_trigger_classifier.py tests/analysis/test_trigger_review.py tests/analysis/test_trigger_readiness.py tests/test_trigger_check.py -> 50 passed
• .venv/bin/python -m pytest -q tests/analysis/test_trigger_review.py tests/analysis/test_trigger_readiness.py tests/analysis/test_trigger_classifier.py tests/analysis/test_trigger_capture.py tests/test_trigger_check.py tests/test_auto_qa_flow.py -> 94 passed
• .venv/bin/python -m pytest -q -k 'not qwen3_compute_loss' -> 280 passed, 6 deselected
• git diff --check origin/main...HEAD
• gsd-tools init progress / roadmap analyze -> 3/3 v1.2 phases complete

Review

• pre-merge agent review found three live-assist/date-filter risks; fixed in follow-up commit
• re-review found no blocking issues