TDD

• Use red/green tests for deterministic logic, state transitions, parsers, policies, asset contracts, and reproduced regressions.
• Keep the narrowest useful test loop running while editing.
• Use the repository's current npm test command as owner truth; do not silently replace or broaden it.
• Rendered behavior requires bounded browser proof in addition to automated assertions. A passing DOM, bbox, asset-load, or screenshot-production check does not prove the visible result.
• Visual acceptance requires opening the exact final capture at original resolution and recording PASS or FIX against the GDD target/reference.
• Performance claims require measured frame timing or resource evidence, not subjective smoothness.
• Do not add a permanent browser suite merely to test pure logic.