fix: keep large-plan interactions off the full render path

Issue: #451
User-Visible: yes

src/render-invalidation.ts

@@ -0,0 +1,68 @@
+/** HA data that can change the painted House Plan frame. */
+export interface HassRenderDependencies {
+  readonly entityIds: Iterable<string>;
+}
+
+export type HassRenderChange = 'none' | 'state' | 'structural';
+
+const scalarChanged = (before: any, after: any, path: readonly string[]): boolean => {
+  let a = before, b = after;
+  for (const part of path) {
+    a = a?.[part];
+    b = b?.[part];
+  }
+  return a !== b;
+};
+
+/**
+ * Classify one HA assignment without walking the complete `hass.states` map.
+ *
+ * Home Assistant keeps unchanged state rows by identity. Comparing only the
+ * dependency rows therefore catches state, attribute and availability changes
+ * while making an unrelated tick O(number of plan dependencies), not
+ * O(number of HA entities). Structural values deliberately fail open: they are
+ * rare and can alter formatting, registry resolution, permissions or actions.
+ */
+export function classifyHassRenderChange(
+  before: any,
+  after: any,
+  dependencies: HassRenderDependencies | null,
+): HassRenderChange {
+  if (before === after) return 'none';
+  if (!before || !after || !dependencies) return 'structural';
+
+  if (before.connection !== after.connection
+      || before.entities !== after.entities
+      || before.devices !== after.devices
+      || before.areas !== after.areas
+      || before.themes !== after.themes
+      || before.user !== after.user
+      || before.config !== after.config
+      || before.floors !== after.floors
+      || before.services !== after.services
+      || before.panels !== after.panels
+      || before.language !== after.language
+      || scalarChanged(before, after, ['locale', 'language'])
+      || scalarChanged(before, after, ['locale', 'number_format'])
+      || scalarChanged(before, after, ['locale', 'time_format'])
+      || scalarChanged(before, after, ['locale', 'date_format'])) {
+    return 'structural';
+  }
+
+  // `states` is the only top-level collection for which this classifier can
+  // prove irrelevance from the dependency projection. A newly introduced HA
+  // capability must therefore fail open until it receives an explicit rule;
+  // otherwise a frontend release could silently leave that UI stale.
+  const compared = new Set([
+    'states', 'connection', 'entities', 'devices', 'areas', 'themes', 'user',
+    'config', 'floors', 'services', 'panels', 'language', 'locale',
+  ]);
+  for (const key of new Set([...Object.keys(before), ...Object.keys(after)])) {
+    if (!compared.has(key) && before[key] !== after[key]) return 'structural';
+  }
+
+  for (const entityId of dependencies.entityIds) {
+    if (before.states?.[entityId] !== after.states?.[entityId]) return 'state';
+  }
+  return 'none';
+}