feat: Implement basic general folder support (#2051)

- Related: #1748

tests/ha/get-entities.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, it } from 'vitest';
+import { getEntitiesFromHASS } from '../../src/ha/get-entities';
+import { createHASS, createStateEntity } from '../test-utils';
+
+describe('getEntitiesFromHASS', () => {
+  const hass = createHASS({
+    'camera.front_door': createStateEntity(),
+    'light.kitchen': createStateEntity(),
+    'light.living_room': createStateEntity(),
+    'sensor.temperature': createStateEntity(),
+    'switch.garage': createStateEntity(),
+  });
+
+  it('returns all entity ids when no domain is specified', () => {
+    expect(getEntitiesFromHASS(hass)).toEqual([
+      'camera.front_door',
+      'light.kitchen',
+      'light.living_room',
+      'sensor.temperature',
+      'switch.garage',
+    ]);
+  });
+
+  it('returns only entities of the specified domain', () => {
+    expect(getEntitiesFromHASS(hass, 'light')).toEqual([
+      'light.kitchen',
+      'light.living_room',
+    ]);
+  });
+
+  it('returns an empty array if no entities match the domain', () => {
+    const result = getEntitiesFromHASS(hass, 'binary_sensor');
+    expect(result).toEqual([]);
+  });
+});