Route provider failures to runtime recovery

[yha9806]

Summary

• route provider_failure fallback_to_agent dry-run decisions to runtime_provider_recovery instead of fallback_agent
• add runtime_recovery fields and counts to dry-run summaries
• surface runtime recovery counts in dry-run and training-effectiveness CLI output

Real-case effect

• recovered dry-run fallback_agent_count: 4 -> 2 after provider failures move to runtime recovery
• runtime_provider_recovery decisions: 2
• residual audit expected boundaries: 2, unexpected fallbacks: 0
• remaining fallback residuals are visual ownership only: occlusion and under_split

Verification

• PYTHONPATH=src python3 -m pytest tests/test_dry_run_decision_router.py tests/test_fallback_residual_audit.py tests/test_real_source_context_recovery_eval.py tests/test_training_effectiveness_report.py tests/test_source_context_gap_pack.py -q
• PYTHONPATH=src python3 scripts/real_source_context_recovery_eval.py --repo-root . --case-source-manifest docs/benchmarks/learning/combined_case_source_manifest_v1.json --artifact-search-root /Users/yhryzy/dev/vulca/.scratch/p2b-live-shipgate --image-search-root /Users/yhryzy/dev/vulca/.scratch/p2b-live-shipgate --source-dependency-manifest docs/benchmarks/learning/real_source_dependency_label_manifest_v1.json --output-dir build/runtime_provider_recovery_v1/real_recovery_eval --report build/runtime_provider_recovery_v1/real_recovery_eval/report.json --max-recovered-source-context-gaps 0 --min-fallback-agent-reduction 2 --min-recovered-eval-cases 2
• PYTHONPATH=src python3 scripts/fallback_residual_audit.py --decision-path build/runtime_provider_recovery_v1/real_recovery_eval/recovered/dry_run/dry_run_decisions.jsonl --report build/runtime_provider_recovery_v1/residual_audit/report.json
• ruff check src/vulca/learning/dry_run_decision_router.py src/vulca/learning/training_effectiveness.py scripts/dry_run_decision_router.py scripts/training_effectiveness_report.py tests/test_dry_run_decision_router.py tests/test_training_effectiveness_report.py
• python3 -m py_compile src/vulca/learning/dry_run_decision_router.py src/vulca/learning/training_effectiveness.py scripts/dry_run_decision_router.py scripts/training_effectiveness_report.py
• git diff --check