[Fix] CodeRabbit skips updates to label-opted PRs

[zoomote]

​Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Enable incremental CodeRabbit reviews for PRs opted in through coderabbit-review-active.
• Keep repository-wide automatic review disabled so required CI still controls when the workflow applies the opt-in label.

Why this change was made

CodeRabbit supports positive-label opt-in while automatic reviews are disabled, but later pushes are reviewed only when incremental review is enabled. With incremental review disabled, PRs such as #1421 showed “Review skipped” after a new head even after the workflow recycled the activation label.

Impact

Human-authored PRs remain ineligible for CodeRabbit until required CI passes and the workflow applies the managed label. Once opted in, subsequent pushes can receive the current-head review required by the review-state workflow.

There is no rendered extension UI change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[github-actions]

Review process

This PR was opened by an automated account. A human maintainer must verify the change intent, provenance, and validation before merging.

1. Required CI checks pass.
2. The workflow starts CodeRabbit automatically.
3. For eligible human-authored PRs, CodeRabbit reviews and approves the latest commit.
4. A human maintainer reviews and approves after CodeRabbit.

Current step: The required review sequence passed. Remaining merge requirements apply.