Feature request: Approve PR when no bugs are found

[Luen]

Add an optional feature to submit an APPROVE PR review when Claude BugBot completes successfully and finds no bugs.

This would match Cursor BugBot's behaviour, where a clean BugBot review can automatically approve the PR.

Suggested behaviour

• Add an opt-in input such as approve-if-clean: true
• When analysis.bugs.length === 0, submit the review with event: "APPROVE" instead of event: "COMMENT"
• If bugs are found, retain the existing comment/review behaviour
• Default to false to preserve current behaviour

This would let Claude BugBot meet PR review/branch protection requirements when its review is clean.