test: coderabbit lock unlock e2e

[sudo-anshul]

E2E smoke test to verify fix for hiero-ledger#2343.

Test sequence:

1. Issue created → Moderate New Issues locks it + adds pending-review
2. Add skill: beginner label → CodeRabbit Plan Trigger should SKIP (locked guard)
3. Add approved label → Approve Issues unlocks → CodeRabbit fires

[github-actions]

Thanks for your submission.

This issue is awaiting approval from @hiero-ledger/hiero-sdk-python-triage and @hiero-ledger/hiero-sdk-python-committers and @hiero-ledger/hiero-sdk-python-maintainers.

[github-actions]

Approved by @hiero-ledger/hiero-sdk-python-triage and @hiero-ledger/hiero-sdk-python-committers and @hiero-ledger/hiero-sdk-python-maintainers.

[github-actions]

@coderabbitai plan