ci: Forward-port manual SHA deploy escape hatch from #1502

[yamcodes]

Summary

Forward-ports merged dev PR #1502 onto v1.

• Adds Deploy www (manual SHA) (workflow_dispatch) so maintainers can deploy any commit to arkenv-dev.vercel.app, arkenv-v1.vercel.app, or production arkenv.js.org without moving the branch.
• Documents the escape hatch (and the Actions/Vercel CLI branch-domain deploy behavior that was already on dev from Safely remove native Vercel Git noise after Actions owns all deploys #1460) in docs/CONTRIBUTING.md.

No package code changes; no changeset.

Source

• Dev PR: ci: add manual SHA deploy escape hatch for stable www URLs #1502
• Merge commit on dev: 4111bda7

Test plan

• Confirm workflow YAML matches dev (paths/secrets identical; no v1 package-layout remap needed)
• After merge: Actions → Deploy www (manual SHA) → known-good v1 SHA → arkenv-v1.vercel.app
• Confirm alias/deploy succeeds in the run log

  

[changeset-bot]

⚠️ No Changeset found

Latest commit: 10c1706

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[pullfrog]

✅ No new issues found.

Reviewed changes — forward-port of the manual SHA deploy escape hatch from dev PR #1502, adding a workflow_dispatch workflow and documenting it for maintainers.

• Add deploy-www-manual.yml workflow — maintainer-triggered workflow_dispatch that deploys any commit SHA to arkenv-dev.vercel.app, arkenv-v1.vercel.app, or production arkenv.js.org via Vercel CLI with git metadata.
• Document the escape hatch in CONTRIBUTING.md — expands the Preview deployments section to describe the Actions/Vercel CLI branch-domain behavior and the new manual SHA deploy option.

  ^{｜ View workflow run ｜ Using DeepSeek Pro (free via Pullfrog for OSS) (GPT Sol not used — the program covers this model; add its provider key to run your pick) ｜ 𝕏}