chore: public logic hardening wave (infra audit)

[VontaJamal]

Summary

• execute infra hardening wave audit for existing public logic only
• add and finalize /docs/audits/public-logic-audit-2026-02-22.md
• close CI coverage gap by adding default-branch public-logic validation workflow

Fixes / Hardening Applied

• added .github/workflows/public-logic-ci.yml for push/pull_request on main
• workflow validates policy JSON, leveling JSON, README link integrity, and governance build path
• documented findings and remediation in audit artifact

Validation

• .seven-shadow/policy.json parse: pass
• leveling.example.json parse: pass
• npm --prefix governance/seven-shadow-system ci: pass
• npm --prefix governance/seven-shadow-system run build: pass
• README/architecture relative link integrity scan: pass

Audit Artifact

• docs/audits/public-logic-audit-2026-02-22.md

No New Feature Attestation

• This PR is maintenance and quality-control only.