feat v1.42.0: room settings — the third settings tier

- four-tier principle fixed in ARCHITECTURE: global > space > room >
  device, specific overrides general, unset inherits
- room.settings { fill_mode, temp_source, hum_source } with backend
  schema; pure roomFillModeOf + sourceValue (+2 test suites, 114)
- gear on room cards in the Plan editor opens Room settings: rename,
  re-area (current area included in the list), fill override (may opt
  out of glow darkness), explicit temp/hum source with a searchable
  device+entity dropdown; the same section in the creation dialog
- source feeds the room card, tooltip and temp fill; works for rooms
  without an HA area (user-feedback case #1)
- smoke_room_settings.mjs (10 checks); TESTING/CHANGELOG/ARCHITECTURE
  same-commit

src/types.ts

@@ -1,8 +1,16 @@
 /** Shared types of the House Plan card. */
 
 export interface RoomCfg {
-  /** Rooms this one has an OPEN (virtual) boundary with — light flows through. */
+  /** Rooms this one has an OPEN (virtual) boundary with - light flows through. */
   open_to?: string[] | null;
+  /** Room-level settings (tier 3 of 4: global > space > ROOM > device). */
+  settings?: {
+    /** Fill override; unset = inherit the space fill mode. */
+    fill_mode?: 'none' | 'lqi' | 'light' | 'temp' | null;
+    /** 'device:<id>' or 'entity:<eid>'; unset = average over the room sensors. */
+    temp_source?: string | null;
+    hum_source?: string | null;
+  } | null;
   id?: string;
   name: string;
   area: string | null;