feat(seo): md alternate tags + copy/ask actions

[pamelachia]

multigres.com serves markdown for every docs page, blog post, and the homepage, but nothing advertised it: agents had to know the .md convention in advance. This adds the discovery layer on top of the Accept/.md negotiation locked in by #71, and standardizes the on-page affordance to Copy Markdown + Ask ChatGPT/Claude.

Changed:

• Agents can discover markdown from any HTML page: docs pages, blog posts, and the homepage now emit <link rel="alternate" type="text/markdown" href="<absolute .md sibling>">. The homepage sibling gains a /index.md URL (the middleware previously only answered /.md), matching the docs-root index.md shape; /.md keeps working.
• llms.txt / llms-full.txt Content-Type is now an explicit contract: both handlers relied on the Fetch-spec default for string bodies (production already served text/plain;charset=UTF-8); the header is now set explicitly so a runtime change can't silently alter it.
• Docs view-options popover replaced by inline actions: the upstream popover hardcodes four extra entries (View as Markdown, Open in GitHub, and two third-party AI tools) with no props to disable them, so the kept entries (Ask ChatGPT, Ask Claude) are now inline links beside the existing Copy button via a shared MarkdownActions component. URL templates, prompt text, and brand icons are byte-identical to what the popover generated.
• Blog posts and the homepage gain the same affordance: both served markdown with zero UI; they now render the same MarkdownActions row.
• Copy/ask/GitHub clicks are measured: ask_ai_clicked (agent: chatgpt | claude), copy_as_markdown_clicked (fires only after a successful clipboard write), and multigres_github_clicked (source: hero | nav | footer). The first two match the supabase.com docs event names so readouts can union both sites and split by host; the GitHub event is deliberately site-prefixed since the supabase.com equivalent (homepage_github_button_clicked) has a different shape, so no name union is possible there anyway. Sent through the existing PostHog client (pageviews already flow; autocapture is off at the project level, so explicit events are required).

Note: placement screenshots (docs header, blog header, homepage hero at desktop + mobile) reviewed before this leaves draft.

To test

Previews are behind Deployment Protection, so pre-merge verification ran against the built Nitro function locally (14-check fetch matrix, all green); the same matrix re-runs as curl against production after merge:

• Alternate tag on /, /docs, /docs/architecture, /blog/listen-notify — each pointing at an absolute .md sibling that 200s as text/markdown
• /index.md serves the homepage markdown; /.md still works
• /llms.txt + /llms-full.txt return text/plain; charset=utf-8 (GET + HEAD)
• Bare */* Accept still gets HTML on docs (no negotiation regression)
• types:check error count unchanged vs main (4 pre-existing); naming lint green
• Vercel preview (authed browser): actions row on all three surfaces, tags present, .md + llms serving verified in-browser
• Preview clicks ingested into PostHog (project 34344, preview $host): ask_ai_clicked agent=chatgpt + agent=claude, copy_as_markdown_clicked after successful clipboard write
• Post-merge: prod curl matrix re-run; spot-check multigres_github_clicked ingestion (same capture path as the verified events)

Linear

• fixes GROWTH-1015

[vercel]

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Project	Deployment	Actions	Updated (UTC)
multigres-site	Ready	Preview, Comment	Jul 28, 2026 5:13pm