Adds a `format-check` target (ruff format --check, no modifications) and makes `test` depend on it — catches unformatted changes before the test suite runs, so agent sessions committing without `make format` fail loudly instead of accumulating silently. One-time sweep over 54 files (1134 insertions / 437 deletions) brings the tree back to a clean baseline. All changes are pure ruff-format output — no lint fixes, no semantic changes. Drift had built up because there was no gate: no pre-commit hook and no pre-test check, only `make ci` (which isn't in the routine loop). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>