release: tolerate annotated release tags

[gaelic-ghost]

Summary

• Compare existing release tags by their resolved commit instead of the annotated tag object SHA.
• Keeps resumed standard release runs from rejecting an annotated tag that already points at the intended release commit.
• Adds maintain-project-repo workflow coverage so the generated toolkit keeps this behavior.

Related socket issues

• Follow-up to Release script should wait for initial PR checks to appear #19, which fixed waiting for initial PR checks before release CI watching.
• Follow-up to Release comment gate should not count approval-only reviews #20, which fixed the release comment gate for approval-only reviews.
• No currently open socket issue exists for this annotated-tag resume bug, so this PR does not include a Closes #... trailer.

Verification

• uv run pytest skills/maintain-project-repo/tests/test_maintain_project_repo_workflow.py
• uv run scripts/validate_socket_metadata.py
• git diff --check