Covers: hex/rgb color detection, spacing detection, variant candidate
threshold logic, toSuggestions ordering, stable IDs, edge cases.
Infra note: tests in tests/models/ — use 'npm run test:editor' not
'npx jest' directly (webpack build required by test-editor.ts script).
'npx jest' alone hangs on webpack. Move tests to tests/models/ not
tests/services/ — transform config only covers models/ path.
