[SandObserver]

Summary

• Add contributing/other-clients.md: cookie sign-in, the Origin header rule for POST, reading /api/version and /api/config, polling on _rev, embedding widget pages, and the no-password Host rule. Marked unstable with no compatibility promise.
• Widget page address: index.html, or the src of the selected view from GET /api/widgets.
• Add an "Other clients" entry to the Contributing sidebar.
• Replace the copied CI check list on the contributing page with a link to CONTRIBUTING.md, whose list a test pins to .github/actions/checks/action.yml.

Testing
npm run build and npm run check pass. Text-only page; no visual check in both themes.

Checklist

• npm run build and npm run check both pass.
• Product UI is shown by running or capturing it, never recreated in CSS.
• Any new preview or screenshot carries no private hostnames or real data.
• Visual changes verified in both colour schemes and both docs themes.
• Links to the app repo still resolve.

[cloudflare-workers-and-pages]

Deploying stackyard-docs with    Cloudflare Pages

Latest commit:	1bca5d9
Status:	✅  Deploy successful!
Preview URL:	https://2088f3b2.stackyard-docs.pages.dev
Branch Preview URL:	https://docs-other-clients-page.stackyard-docs.pages.dev

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