docs: adopt solo-maintainer governance

[fly1d]

Outcome

Makes the repository review policy executable for a one-person company without weakening PR, CI, smoke, rollback, or production-safety evidence. Separates an owner risk decision from independent review and separates code merge from production approval.

Closes #22

Evidence

• make check passes: 32 passed, 1 local PostgreSQL test skipped without ACP_DATABASE_URL, 98.55% coverage
• Compatibility impact reviewed: governance and PR-template changes only
• Monitoring or audit impact reviewed: no runtime impact
• Policy explicitly rejects alternate-account and AI-generated pseudo-approval

Risk

• Level: low
• Failure mode: ambiguous wording could let high-risk code be mistaken for production-approved code.
• Rollback plan: revert this documentation-only commit and restore the prior team-only policy.

Review decision

• Mode: solo-maintainer governance bootstrap
• Independent reviewer(s), if required: not available; this PR replaces the currently unsatisfiable rule
• Final material push: not applicable for low-risk documentation
• Earliest merge: after required CI passes
• High-risk production status: not applicable
• Owner decision: merge; explicitly approved by repository owner on 2026-08-14 and recorded in Adopt solo-maintainer review governance #22

This is the single bootstrap exception to the previous one-approval rule. Subsequent PRs follow the policy introduced here.

Release notes

None; repository governance only.