Add two tests to verify that issue blocking/dependencies are enforced
when closing issues via the RPC handler:
- TestHandleClose_BlockerCheck: Verifies closing a blocked issue fails
when blocker is still open, and --force flag overrides the check
- TestHandleClose_BlockerCheck_ClosedBlocker: Verifies close succeeds
once the blocking issue is closed
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>