docs: warn about Date coercion in CRUD callback inputs

[MMMikeM]

Summary

• Adds JSDoc to create, update, and delete on SyncedCrudPropsBase warning that fields named by fieldUpdatedAt/fieldCreatedAt will be Date at runtime, not the declared type

clone() uses a JSON reviver that converts ISO 8601 strings to Date objects. When fieldUpdatedAt or fieldCreatedAt is set, the corresponding fields on the callback input parameter are Date at runtime — but the TypeScript types still reflect the original declared type (e.g. string or number). This can cause silent failures when passing those values to APIs that expect strings.

The JSDoc surfaces this in the IDE on hover so consumers are aware of the mismatch.

Test plan

• No type or runtime changes — JSDoc only

[MMMikeM]

Reproduction: runtime Date coercion in CRUD callbacks

test('fieldUpdatedAt field is Date at runtime despite string typing', async () => {
    let receivedInput: any;

    const obs = observable(
        syncedCrud({
            initial: { a: { id: 'a', updatedAt: '2024-01-01T00:00:00.000Z' } },
            fieldUpdatedAt: 'updatedAt',
            update: async (input) => { receivedInput = input; },
        }),
    );

    await promiseTimeout(1);
    obs.a.set({ id: 'a', updatedAt: '2025-01-01T00:00:00.000Z' });
    await promiseTimeout(1);

    // TS says input.updatedAt is `string`, but clone()'s JSON reviver converts it
    expect(receivedInput.updatedAt).toBeInstanceOf(Date);
});

This passes — confirming the type/runtime mismatch the JSDoc warns about.