What

Improve the desktop release Cloudflare cache purge steps and switch them to a dedicated purge token secret.

Why

The nightly desktop build failed after publishing artifacts because the final Cloudflare purge call was brittle and the existing token setup was not scoped for cache purge. This keeps release publication reliable while avoiding reuse of unrelated Cloudflare credentials.

How

• switch desktop build/release workflows to CLOUDFLARE_PURGE_API_TOKEN
• add retry, backoff, HTTP status capture, and response-body logging around the purge request
• fail only when all purge attempts are exhausted or Cloudflare returns a non-success response
• locally validate the updated logic with a retrying mock server and a real Cloudflare purge request against the nightly latest artifacts

Affected areas

• Desktop app (Electron shell)
• Controller (backend / API)
• Web dashboard (React UI)
• OpenClaw runtime
• Skills
• Shared schemas / packages
• Build / CI / Tooling

Checklist

• pnpm typecheck passes
• pnpm lint passes
• pnpm test passes
• pnpm generate-types run (if API routes/schemas changed)
• No credentials or tokens in code or logs
• No any types introduced (use unknown with narrowing)

Notes for reviewers

• Added repo secret: CLOUDFLARE_PURGE_API_TOKEN
• Verified the new token with a real purge call for nightly latest artifacts before opening this PR