docs: Capture release-note editorial and validation guidance

[T-Gro]

Summary

Capture generic user guidance in the existing milestone release-notes pipeline.

• Discover omissions from pinned shipped changes and source tests. Compare actual predecessor articles and omit unchanged announcements.
• Preserve official feature names, explicit priorities, audience distinctions, and accurate preview requirements. Allow concrete benefit-focused narrative.
• Separate application and compiler performance stories. Keep metrics, baselines, source-built scope, regressions, and evidence limits clear.
• Validate claims in scratch storage by default. Commit maintained fixtures only within explicit scope. Keep article/report imports and PR updates within approved publication boundaries.
• Require evidence of reviewer comparisons and strict link checks, not assumed panel results or HTTP 429 passes.

Scope

Documentation only: seven writer/template/editorial/validation/review instruction files, plus one sentence in the schema reference. That sentence preserves strict new-release provenance while linking the canonical rules for explicitly requested catch-up coverage and full-cycle reports.

No release articles, release metadata, historical example files, samples, compiler code, workflows, scoring rubric, or model preferences changed. This is a separate documentation PR, not a release-article update.

Checks

• Markdown lint and whitespace checks passed.
• Strict link checks passed for all eight files, with no ignored targets and only HTTP 200 accepted.
• Checked 40 rendered relative references, including five heading anchors. Confirmed the existing GitHub PR citation through the authenticated API.
• Confirmed unchanged fenced examples and skill frontmatter.
• Checkov: 446 passed, zero failed; one parsing warning in unchanged release metadata.
• Prettier: two format warnings, also present in the unchanged main baseline. Left those baseline issues unchanged.

Capture-to-policy coverage and validation records remain in session storage, outside this PR.