v0.12.2 — @loupe review reports completion

@loupe review now tells you when it is done

Each reviewer keeps one summary comment per PR and updates it in place. That is what makes incremental review work, but it made a forced re-review invisible: @loupe review posted "🔍 On it", the summaries higher up the thread changed silently, and nothing new appeared. On a PR outside the config's dir, every reviewer found zero files, posted nothing, and the ack stayed forever.

The ack is now edited into a completion line when the run finishes:

✅ Re-review of `c61996e` done.

- code: ✅ no issues
- zdr: 🟡 1
- docs: ✅ no issues

Each reviewer's summary comment above was updated in place.

or, when no changed file is under the config's dir:

Nothing to review: this loupe config covers `inference/` and no changed file is under it.

A reviewer that failed shows ⚠️ failed (see the failure comment).

Internals

• runReviews returns one outcome per reviewer instead of a boolean.
• postIssueComment returns the comment id; new updateIssueComment.
• Docs: docs/how-it-works/chat.md.