test: Python test parity — add missing test files

[Rome-1]

What

Python has ~13 fewer test files than Node. Each missing file is a self-contained contribution opportunity.

Missing Python test files

Pick any one and submit a PR. Each is independent:

File to create	Node reference	Effort
`tests/test_formatter.py`	`node/tests/formatter.test.ts`	~1 hour
`tests/test_git_utils.py`	`node/tests/git-utils.test.ts`	~1.5 hours
`tests/test_api_utils.py`	`node/tests/api-utils.test.ts`	~1 hour
`tests/test_binary_manager.py`	`node/tests/binary-manager.test.ts`	~2 hours
`tests/test_brief.py`	See #28	~1.5 hours

How

1. Read the corresponding Node test file
2. Port the test cases to pytest
3. Ensure feature parity — same scenarios, same assertions
4. Run: `cd python && pytest tests/test_.py -v`

Notes

• Each test file is a standalone PR — no need to do all at once
• Follow existing Python test conventions in `python/tests/`
• Both implementations must have identical behavior per `shared-docs/CLI_SPEC.md`