ci: report conclusion for PRs that ci.yaml skips

[akern40]

ci.yaml uses paths-ignore to skip PRs that only touch .github/workflows/latest-deps.yaml. Since conclusion is a required check, such PRs can never merge. The check just sits at "Expected — Waiting for status to be reported", as on #1623.

This adds a small workflow that runs only for those paths and reports a conclusion job of its own. It passes only if every changed file is one that ci.yaml ignores. If a PR also touches other files, the real CI runs as well and this job fails, so it can't stand in for a real failing conclusion. The paths list has to stay in sync with ci.yaml's paths-ignore.

Link to Devin session: https://app.devin.ai/sessions/4b52e943e29a466ea652d856b7f556c4
Open in Devin Desktop: https://app.devin.ai/desktop/session/4b52e943e29a466ea652d856b7f556c4?variant=devin
Requested by: @akern40

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access that start with 'Devin'.

• Disable automatic comment, CI, and merge conflict monitoring