Persist bounded AV1 failure classifications

[cbusillo]

Summary

• bump AV1 v4r3 ordinal outcomes to schema v2 with closed failure phase, class, and search-status tokens
• preserve exact schema-v1 readability while rejecting malformed v2 outcomes
• classify and persist production-search/runtime-identity failures without exception text, paths, argv, stderr, CRF values, media facts, or raw traces
• preserve absorbing terminal behavior and re-raise interpreter interrupts after persistence

Validation

• uv run --with pytest pytest tests/test_av1_validation_v4r3_one_ordinal_runner.py tests/test_av1_validation_v4r3_ordinal_window.py -q (46 passed, 9 subtests passed)
• bash scripts/pre-commit-check.sh (2515 collected; full backend/frontend/build/smoke gate passed)
• commit hook reran the full acceptance gate successfully
• Opus final re-review: APPROVE, no blockers
• Gemini review attempted twice; both returned empty output and are not represented as approval

Closes #395