docs: add reusable notice content type

[sbvegan]

What changed

• Added a reusable notice content-type contract and copy-paste template for time-bound upgrade, deprecation, and operational notices.
• Classified notices as Diátaxis reference pages, with content_type: notice reserved for their operational purpose and lifecycle rather than treated as a fifth quadrant or composition.
• Extended the content-type chooser and contributor landing page with notice guidance.
• Added the notice template to documentation navigation.
• Normalized active and archived notice frontmatter with the notice content type.

Why

Network changes need a consistent public-documentation shape that identifies affected personas, breaking changes, required actions, timing, transition behavior, verification, support, and archive handling. The reusable contract gives authors and reviewers a shared standard while keeping the existing four-quadrant Diátaxis taxonomy intact.

This work was split from #22092 so the reusable documentation model can be reviewed independently from the Upgrade 20 notice.

Verification

• node --import tsx scripts/lint/validate-nav.ts
• node --import tsx scripts/lint/validate-redirects.ts
• node scripts/lint-link-policy.mjs --baseline scripts/lint-link-policy.baseline.json
• git diff --check

Reviewer checklist

• Confirm that a notice is correctly classified as reference content.
• Confirm that content_type: notice is clearly distinguished from the four content-type: compositions.
• Confirm that the required components cover authoring, review, publication, and archive needs.
• Confirm that the template is reusable across upgrades, deprecations, and operational changes.

[mintlify]

Preview deployment for your docs. Learn more about Mintlify Previews.

Project	Status	Preview	Updated (UTC)
Optimism-Docs	🟢 Ready	View Preview	Jul 29, 2026, 11:55 PM