The docs link drift guard (test_repo_docs_link_drift.py) fails CI because
render_release_body.py links docs/CODE_SIGNING_POLICY.md at blob/main.
Release bodies must reference the docs snapshot of the release they
describe, so the installation section now links blob/v{version}, matching
how the rest of the body pins to the version being cut. The unit test pin
follows. Also skip .claude/ in the drift guard so local runs on a shared
tree are not polluted by stale agent worktrees under .claude/worktrees
that CI never checks out.
