[Improve] Show reviewing/reviewed status footer on PR review comments

[roomote-roomote]

Opened on behalf of Matt Rubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

Related issue

Internal product follow-up from Slack; no tracked issue.

Why this PR exists

• A maintainer explicitly invited this PR in the linked issue or discussion
• I am a maintainer / this is internal Roomote work

What changed

Main Roomote PR review summary comments now end with a small visible status footer:

<sub>Reviewing #shortsha at YYYY-MM-DD HH:MM:SS UTC</sub> while the review is running, and Reviewed once it completes.

The short SHA links to the commit when a GitHub commit URL can be built, and the footer is wired through initial create/reuse, agent skill instructions, and the terminal safety-net finalizer.

How it was tested

• Unit tests for the footer builder, body assembly (including comment-reuse SHA/link alignment), terminal finalization, and review-skill contract text
• pnpm lint and pnpm check-types (pre-push also passed lint:fast / check-types:fast / knip)

Checklist

• The PR title follows the repo convention: [Fix], [Feat], [Improve], [Refactor], [Docs], or [Chore] followed by a user-facing description
• This PR is small and scoped to one change
• pnpm lint and pnpm check-types pass locally
• I added tests or included a clear manual validation note above
• I removed secrets, tokens, private keys, and customer data from code, logs, and screenshots
• If this change should appear in the changelog, I ran pnpm changeset

[roomote-roomote]

No code issues found. See task