fix(dag): enforce deep review terminal gates

[LeXwDeX]

Description\n\nDeep review lifecycle validation accepts a graph ending at a diff review. A structured REJECT is still persisted as NodeCompleted, so a deep workflow can finish successfully without a final gate or correction path.\n\nSeverity: HIGH (release blocker).\n\n## Reproduce\n\n1. Create a deep graph: implementation → verification(PASS) → diff review.\n2. Omit any downstream final audit/gate.\n3. Return a valid REJECT payload from the review node.\n4. The review node completes and the workflow can reach completed.\n\n## Acceptance\n\n- Deep diff-review topology cannot end without a downstream terminal gate/audit.\n- A REJECT cannot produce a successful workflow completion without a correction/reverification/re-review path.\n- ACCEPT remains bound to the current implementation fingerprint.\n- Tests cover missing final gate, REJECT, correction, and stale fingerprints.\n

[LeXwDeX]

已由 PR #148 修复，并通过 PR #149 晋级 main。deep review 最终门禁及显式 complete 防绕过已覆盖回归测试，最终双轴 review 无 CRITICAL/HIGH。