docs(backlog): reconcile protected merge evidence

[aatuh]

Summary

• mark TST-003 complete only after protected implementation PR test(redis): validate supported adapters on real redis #109 merged
• record exact squash SHA c94cadaf0865da371b23f7cda9e2def65d83c99b and its green check evidence
• record strict branch-protection requirements for the PostgreSQL and Redis contract jobs
• preserve the explicit server-restart/failure-injection boundary

Validation

• GOWORK=off GOTOOLCHAIN=local make docs-site
• GOWORK=off GOTOOLCHAIN=local make docs-check

Refs: TST-003