Wire V2 promotion into production binary:
- Add --block.v2Promotion CLI flag on weed master (default false)
- MasterOption.BlockV2Promotion → NewMasterServer wires flag + querier
- defaultBlockVSQueryEvidence placeholder (returns explicit error until
proto regen on M01 enables gRPC evidence RPC)
Fix three fail-closed violations found by tester:
1. blockV2Promotion=true + nil querier now fails closed with explicit
log instead of silently falling back to V1
2. Partial evidence (any candidate query failed) now fails closed —
unreachable candidate may be the most durable, promoting from
incomplete evidence violates durability-first ordering
3. Clear EngineProjectionMode in applyPromotionLocked (already in
previous commit, verified in tests here)
2 new tests: NilQuerier_FailsClosed, PartialEvidenceFailure_FailsClosed.
Total T3 tests: 7, all pass. Existing V1 failover tests unaffected.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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