fix: preserve backdrop continuity during summary recovery (#490)

Issue: #490
User-Visible: yes

src/summary-panel-host.ts

@@ -49,6 +49,14 @@ export interface SummaryPanelHost extends Node {
   _layoutRev: number;
   _cfgContentFingerprint: string;
   _regSignature: string;
+  _signer: {
+    prepareImage(hass: SummaryHass | undefined, href: string): Promise<boolean>;
+  };
+  _continuity: {
+    readonly hasCompleteFrame: boolean;
+    readonly state: string;
+    note(event: string): void;
+  };
   _writesPending: number;
   _writeChain: Promise<void>;
   _kiosk: boolean;
@@ -73,10 +81,14 @@ export interface SummaryPanelHost extends Node {
   }): Promise<boolean>;
   _sendConfigCandidate(candidate: ServerConfig): Promise<void>;
   _getAuthoritativeConfig(): Promise<AuthoritativeConfigResponse>;
+  _candidateBackdrop(config: ServerConfig | null): string;
+  _scheduleLoadRetry(force?: boolean): void;
+  _beginContinuityCandidate(reason: string, dataReady: boolean): number;
   _adoptStructuralResponses(response: AuthoritativeConfigResponse): { configChanged: boolean };
   _syncDecorAssets(config: ServerConfig | null): Promise<void>;
   _adoptInitialSpace(models: SpaceModel[], authoritative?: boolean): unknown;
   _maybeRebuildDevices(): void;
+  _resumePendingNavMode(): boolean;
   _restoreZoom(): void;
   _reloadConfigOnly(force?: boolean): Promise<void>;
   _cacheSnapshot(): void;

src/summary-panel-runtime-loaded.ts

@@ -440,10 +440,24 @@ export class LoadedSummaryPanelRuntime {
               const authoritative = await this.host._getAuthoritativeConfig();
               const confirmed = confirmedSummaryPanelWriteRecovery(authoritative, draft);
               if (!confirmed) throw writeError;
+              const configChanged = contentFingerprint(confirmed.config)
+                !== (this.host._cfgContentFingerprint || contentFingerprint(this.host._serverCfg));
+              if (configChanged && !await this.host._signer.prepareImage(
+                this.host.hass, this.host._candidateBackdrop(confirmed.config),
+              )) {
+                this.host._continuity.note('asset-failed');
+                this.host._scheduleLoadRetry(true);
+                throw writeError;
+              }
+              if (configChanged && this.host._continuity.hasCompleteFrame
+                  && this.host._continuity.state === 'steady') {
+                this.host._beginContinuityCandidate('summary-recovery', true);
+              }
               const visibleSpace = this.host._space;
               this.host._adoptStructuralResponses(authoritative);
               void this.host._syncDecorAssets(confirmed.config).catch(() => undefined);
               this.host._adoptInitialSpace(this.host._model, true);
+              this.host._resumePendingNavMode();
               this.host._cacheSnapshot();
               if (this.host._space !== visibleSpace) this.host._restoreZoom();
               this.host._regSignature = '';