Is your feature request related to a problem? Please describe.
The current tools do not allow AI to navigate git history.

Describe the solution you'd like
Add tools so that AI can execute safe git commands.

"Safe" means:

• Read-only tools only. No history mutation or network I/O.
• Expose specific typed tools, not a free-form command string. Examples:
  • git_log(path=...)
  • git_show(rev=...)
• Tool arguments should be thoroughly validated.
• No subprocess with shell=True.
• The git commands should run in the docker container, not the source.
• Bounded output. Follow the same caps as the other tools and indicate truncation (check grep() and read_file()).

Consider whether the tools being added provide exclusive value or pollute the context window.

Tests:

• Add end-to-end tests for every new tool to tests/ai_code_review/test_tools.py.
• Follow the existing patterns:
  • Use the review session fixture
  • Pin behavior against PINNED_COMMIT
  • Add both happy-path cases and error cases (invalid rev, path outside tree, etc.).