[M5] Create the public beta launch checklist

[igbopharaoh]

Tracking

• Milestone: M5 - Public Beta Readiness
• Suggested labels: priority:p0, type:ops, area:product, milestone:public-beta

Context

Create the release gate for inviting maintainers outside the core team.

Scope

• Define beta success criteria.
• Select initial test repositories.
• Prepare maintainer onboarding documentation.
• Prepare contributor-facing expectation copy.
• Confirm support and debugging channel.
• Record known limitations, rollout, and rollback steps.

Acceptance criteria

• The team can make an explicit evidence-based public beta decision.
• Beta users know what PRGuard does and does not do.
• Known risks and rollback steps are documented.

Validation

• Run the checklist with the core team before sending any beta invitation.

Definition of done

• Relevant Rust, API, or web tests pass.
• Documentation and runbook notes are updated when behavior changes.
• The pull request includes a concise manual verification note.