feat(workbench): submit through an Awesome PR with no local state, and look up its status

[cinderzhan]

Summary

Stacked on #497 (which includes #496). Review only the last two commits.

• Submission keeps no local state. Opening a pull request on dataelement/awesome-dsh-workbench is the submission, so the local submission queue (submissions.mjs), its /api/desktop-workbenches/submissions route and the local-draft UI are removed. An existing submissions.json from an earlier build is neither read nor deleted.
• Guide and prompt follow the Awesome protocol: one data/workbenches/<owner>__<repo>.yml with description.zh + description.en, 1–5 screenshots declared in the YAML, optional tarball, no generated fields.
• PR status lookup. Step 3 of "Make my workbench" accepts a pull-request link from the market repository and shows open / draft / changes requested / merged / closed. The host reads it from the GitHub API without a token and stores nothing; other URLs are refused.

Test plan

• npx vitest run: 133 files, 1198 tests pass; npm run typecheck clean; guide copy matches its source.
• PR status checked against real PRs in awesome-dsh-workbench (Add English README and Chinese translation #1 → draft, Disable implicit builder publishing #3 → merged).

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