yellow means working: one principle for the glowing icon

Research on the owner's install (verified live): the radiator heads that
glowed yellow were the ones with SCALE PROTECTION on, and the ones actually
heating stayed dark. Cause: the primary-entity search ran domains outside
tiers, and switch outranks climate — so a vendor's config switch (anti
scaling, child lock) became the device's primary, driving the color, the
icon morphing and tap-toggle alike.

The principle now: yellow = the device is doing its main job RIGHT NOW.

- primaryEntity: tiers outside, domains inside — a service entity never
  beats the visible main function; a hidden lamp still beats a visible
  config switch (grouped lights), and a plug's switch stays primary.
- climate joins the state table: yellow by hvac_action (heating/cooling/
  drying/fan) — 'which radiators are heating', not 'enabled for winter';
  the coarser state is only a fallback when the integration reports no
  action.
- one truth for light: litLightEntity() is asked by BOTH the glow pool and
  the icon color, in every fill mode — the pool and the icon can no longer
  disagree. The 'is a light source' flag keeps counting controls first.
- README (en+ru): the color table, in words.

Tests: TRV + plug primary units, litLightEntity unit, smoke_yellow_principle
(heating yellow / idle dark / off dark / fallback / lit-light wins / forced
source). Inventory: 142 / 51 / 43 / 67.

test/devices.test.mjs

@@ -1,6 +1,6 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
-import { buildDevices, lightGroups, primaryEntity, lqiFor, tempFor, humFor, areaLights, areaTemp, areaHum, areaLightStats, sourceValue , areaClimate, areaClimateMap } from '../test-build/devices.js';
+import { buildDevices, lightGroups, primaryEntity, lqiFor, tempFor, humFor, areaLights, areaTemp, areaHum, areaLightStats, sourceValue , areaClimate, areaClimateMap, litLightEntity } from '../test-build/devices.js';
 import { compileIconRules, iconFor } from '../test-build/rules.js';
 
 /** Minimal fake hass around the pieces buildDevices reads. */
@@ -483,3 +483,44 @@ test('areaClimateMap: температура и влажность живут в
   };
   assert.deepEqual(areaClimateMap(hass).get('hall'), { temp: 21.4, hum: 48 });
 });
+
+
+test('primaryEntity: a service switch never beats the visible main function (TRV)', () => {
+  // the owner's radiator heads, verified live: switch outranks climate in the
+  // domain list, and the old inner-tier loop let a CONFIG switch (anti
+  // scaling, child lock) become primary — the icon glowed yellow because
+  // scale protection was on, while the head actually heating stayed dark
+  const hass = {
+    entities: {
+      'climate.trv': {},
+      'sensor.trv_temp': {},
+      'switch.trv_anti_scaling': { entity_category: 'config' },
+      'switch.trv_child_lock': { entity_category: 'config' },
+    },
+    states: {},
+  };
+  assert.equal(
+    primaryEntity(hass, ['switch.trv_anti_scaling', 'switch.trv_child_lock', 'climate.trv', 'sensor.trv_temp'], 'mdi:thermostat'),
+    'climate.trv',
+  );
+  // but a device whose only functional entity IS a switch keeps it
+  const plug = { entities: { 'switch.plug': {}, 'sensor.plug_power': {} }, states: {} };
+  assert.equal(primaryEntity(plug, ['sensor.plug_power', 'switch.plug'], 'mdi:power-socket'), 'switch.plug');
+});
+
+test('litLightEntity: one truth for "this thing is shining"', () => {
+  const hass = { states: {
+    'light.a': { state: 'off' }, 'light.b': { state: 'on' },
+    'switch.wall': { state: 'on' }, 'sensor.x': { state: '5' },
+  } };
+  // a lit light.* anywhere in the device
+  assert.equal(litLightEntity(hass, { entities: ['light.a', 'light.b'] }), 'light.b');
+  assert.equal(litLightEntity(hass, { entities: ['light.a'] }), null);
+  // without the flag a lit switch is NOT a light
+  assert.equal(litLightEntity(hass, { entities: ['switch.wall'] }), null);
+  // with "is a light source" any lit entity counts, controls first
+  assert.equal(
+    litLightEntity(hass, { entities: ['sensor.x'], marker: { is_light: true, controls: ['switch.wall'] } }),
+    'switch.wall',
+  );
+});