Frontend: cover config + domain logic, enforce a jest coverage gate

[mandarwagh9]

What & why

The frontend had only 2 smoke tests and no enforced coverage — the biggest remaining "tested and checked" gap. This adds real logic tests plus a jest coverage threshold.

🌿 Parallel to the backend stack — based on #4 (the PR that introduced the frontend test infra), not stacked on the Phase-B chain, so it reviews independently. Auto-retargets to main when #4 merges.

Changes

• Export getIFFColor + estimateDistance from CameraDisplay.jsx so the pure HUD helpers are testable without the canvas.
• Tests (config/index.test.js, CameraDisplay.helpers.test.js):
  • config layer — getConfig path resolution + defaults + dead-end fallback, the WS/API URL builders, validateConfig, getFullConfig
  • HUD helpers — IFF colour by prediction method (HOMOGRAPHY→green, WORLD→orange, EXTRAP→red, homography_source fallback), distance-from-bbox-height (null guard, reference value, inverse relationship)
• package.json — jest coverageThreshold on the logic layer (config + domain): statements/lines ≥ 55%, branches ≥ 45%, functions ≥ 30%; test:ci now runs --coverage.
• .gitignore the jest coverage/ output dir.

Verification

• 29 frontend tests pass (was 14); npm run build clean (eslint).
• Logic-layer coverage 63% statements (gate at 55%).

Notes

Coverage is scoped to the pure-logic layer (config + domain). The canvas rendering in CameraDisplay (drawing functions, lines 46–490) and the hooks/adapters are a known gap better suited to component/e2e tests — a natural next ratchet.

🤖 Generated with Claude Code