Publish a crate stability matrix and release checklist

[blackopsrepl]

Summary

Workspace readiness varies by crate and feature, but that variance is not captured in a standard stability or release document.

Problem

Users currently lack a clear contract for what is mature, experimental, or template-oriented.

Why This Matters

Release expectations should be explicit both for users and maintainers.

Proposed Work

• Add a workspace-level stability matrix covering stable, experimental, and template-only surfaces.
• Define a release checklist that includes at least fmt, clippy, test, and scaffold smoke validation.

Acceptance Criteria

• Stability and readiness expectations are documented.
• Release validation is repeatable and explicit.

Source

Derived from PR #3 (PRODUCTION_REVIEW_ISSUES_2026-03-20.md).

[blackopsrepl]

Resolved by #24.

We added a root RELEASE.md guide with the crate stability matrix, publish order, and release checklist, corrected the beta companion crate guidance for facade version bumps, switched the manual release gates to --all-features, and documented staged real cargo publish --dry-run checks instead of a fake workspace dry-run.