feat: add equals option to watch

[seekskyworld]

Issue link:

• Custom equality for watch #13242

Summary:

• add optional equals comparator to watch (v3 API) to control change detection
• skip callback and cleanup when equals reports equal; warn when used without a callback or with a non-function
• add unit test covering cleanup suppression with equals

Motivation:

• allow semantic equality to prevent unnecessary cleanup/abort when inputs are recreated but equivalent

Validation:

• pnpm test:unit -- test/unit/features/v3/apiWatch.spec.ts