improvement(seo): list the v2 API as a catalog item and answer markdown 404s

[waleedlatif1]

Summary

• API catalog (/.well-known/api-catalog) now opens with a context anchored at the catalog itself that lists the v2 API as an item (RFC 9727 §3.1, Appendix A.2 shape); the existing service-desc / service-doc / status context is unchanged
• Unknown pages answer Accept: text/markdown with a Markdown 404 (text/markdown, Vary: Accept, no-store) linking home, docs, llms.txt, and the sitemap
• Done with a fallback rewrite in next.config.ts gated on the Accept header, so it only runs after every page and dynamic route fails to match: browsers keep the HTML not-found page, real pages and RSC requests are untouched, and /api/* keeps its JSON 404
• Existing rewrites move to afterFiles, which is what the plain array form already meant

Type of Change

• Improvement

Testing

• apps/sim/scripts/test-mcp-host-e2e.ts against a local dev server: 18/18, with new checks for the catalog item context, the Markdown 404 (flat and nested paths), the browser HTML 404, a real page with a Markdown Accept, and /api/* keeping JSON
• Reverted each fix and watched its checks fail (catalog checks without the item context, Markdown 404 checks without the fallback rewrite)
• bun run lint, check:source-conventions, check:api-validation:strict, check:comment-hygiene, check:unused-exports, check:file-names

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Oct 15, 2026 8:15pm UTC

[cubic-dev-ai]

All reported issues were addressed across 4 files

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[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no new blocking issue was found.

Summary

Adds the v2 API as a catalog item and serves Markdown 404s through a fallback rewrite.

• The API catalog lists the v2 API as an item.
• Unknown pages return Markdown 404s to Markdown clients.

_{Reviews (2) · Last reviewed commit: "fix(seo): keep the HTML 404 for clients ..." · Reviewed by Greptile}

[waleedlatif1]

@greptile

[waleedlatif1]

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[cubic-dev-ai]

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[cubic-dev-ai]

All reported issues were addressed across 4 files

<sub>Reply with feedback, questions, or to request a fix.

Turn on auto-fix | Re-trigger cubic</sub>