Summary:
This PR fills critical governance documentation gaps identified during the v5.0 audit and Grok's line-by-line verification.

Changes:
- Add HCB incentive & slashing model (HCB_INCENTIVES_v5.md)
- Add privacy tradeoffs & ZK templates (PRIVACY_TRADEOFFS.md)
- Add legal considerations checklist (LEGAL_CONSIDERATIONS.md)
- Add social red-team playbook (SOCIAL_REDTEAM_PLAYBOOK.md)
- Add test->fix matrix (tests/test_to_fix_matrix.csv)
- Add emergency commit-reveal & rollback snippet (UPGRADE_AND_EMERGENCY.md)
- Append: dashboard spec & HCB demo harness snippets to STRESS_TEST_REPORT_V1.0.md & Protocol_ST8_Access_Decoupling.md

Checklist:
- [ ] Security review (TSC)
- [ ] Two independent auditors (names)
- [ ] Update DECISION-LOG.md with PR reference
- [ ] Merge only after 2/3 reviewer approval

Notes:
Please run the governance CI (/.github/workflows/governance-check.yml) included in this PR to verify doc presence and basic formatting before merging.
