[v1.0] Expand maintainer capacity and document project governance

[codeforester]

Goal

Reduce bus-factor risk and make contribution and release decisions sustainable.

Scope

• Document maintainer roles, review expectations, release ownership, and security escalation.
• Define a path for adding co-maintainers and trusted reviewers.
• Publish decision records for API, contract, and compatibility changes.
• Add contributor onboarding for issue triage, local validation, and release rehearsal.
• Track response and review health as the project grows.

Acceptance criteria

• Governance and maintainer responsibilities are discoverable from CONTRIBUTING.md.
• At least one additional trained reviewer can run the quality and release gates.
• Security and release continuity do not depend on one person.
• Governance changes are reflected in the support and API-stability policies.

Project fields

• Status: Backlog
• Priority: P2
• Area: Product
• Initiative: Adoption Polish
• Size: M