/code-review ultra fails with "no commits yet" despite valid commit history

Description

Running /code-review ultra (no arguments) fails reproducibly with:

Your current branch has no commits yet, so there is nothing to review. Commit your changes first, then rerun /code-review ultra.

...despite the repo having a valid, non-empty commit history.

Repro / verification steps taken

• git log --oneline -5 shows 10 commits on main, most recent well-formed and authored normally.
• git status shows a clean working tree, branch up to date with origin/main.
• Ran /code-review ultra 3 times, including once after git push to sync local main with origin/main — the error is identical every time.
• Checked for anything unusual that might confuse detection: not a shallow clone (git rev-parse --is-shallow-repository → false), git worktree list shows only the single expected worktree, .git/HEAD correctly points to refs/heads/main, git config user.name/user.email are set, git rev-parse HEAD resolves to a real commit.
• No open PR for this branch (checked via gh pr list / gh pr view).

None of these checks turned up anything that would explain the command treating the branch as having no commits.

Expected behavior

/code-review ultra should detect the existing commit history and run the review (per its own docs: "the no-arg form bundles the local branch and does not need a GitHub remote").

Environment

• Claude Code: 2.1.233
• OS: macOS 15.7.7 (24G720)
• git: 2.39.5 (Apple Git-154)
• Repo: local clone with a GitHub remote configured, main branch, local commits ahead of / then synced with origin/main