ultrareview (no-arg): misleads users into thinking it reviews the full codebase

Problem

When a user runs /ultrareview (no-arg form) on a branch with only a trivial 1-line commit, the review runs successfully but reviews only that single line — returning empty findings. This is technically correct behavior (it reviews the branch diff vs main), but it is not communicated clearly to the user beforehand, and Claude Code itself contributed to the problem by assisting in creating a trivial commit specifically to trigger ultrareview without warning the user about the limitation.

User impact

• The user had been saving a limited free ultrareview credit specifically for a pre-public codebase-wide quality check
• Claude Code (the assistant) created a 1-line comment commit and ran /ultrareview on it without clarifying that it would only review that 1-line diff
• The result was 0 findings, the credit was consumed, and the intended review never happened
• User cannot file a bug report about Claude Code's misleading behavior through the normal issue tracker

What Claude Code should do differently

1. Before running /ultrareview (no-arg): check the size of the diff and warn if it is trivially small (e.g., < 5 lines changed, 1 file)
2. When user asks "can ultrareview review the whole codebase?": clearly answer "No — it only reviews the diff between the current branch and main" instead of finding a workaround that wastes a credit
3. Skill documentation: the ultrareview skill description should explicitly state the diff-only scope so the assistant can give accurate guidance

Steps to reproduce

1. Create a branch with only a 1-line commit vs main
2. Ask Claude Code "can ultrareview review the entire codebase?"
3. Claude Code creates a trivial commit and runs /ultrareview without warning
4. Review runs, returns empty findings, credit consumed

Expected behavior

Claude Code warns: "ultrareview only reviews the diff on this branch (currently 1 line). This will not give you a full codebase review. Proceed anyway?"

Environment

• Claude Code CLI
• /ultrareview no-arg form (branch diff mode)