feat: dark mode fix, call wallpaper, setTheme error handling, Sentry filter

- CallEmbed: inject :root { color-scheme } into iframe so EC respects Cinny
  theme regardless of OS preference (fixes white background in dark mode)
- CallEmbed: store themeKind, update color-scheme CSS on live setTheme() calls
- CallEmbed: catch transport.send() rejection in setTheme() to prevent
  unhandled promise rejection when widget not ready yet (fixes REACT-8)
- CallEmbed: html + body both set to background:none so wallpaper shows through
- CallEmbedProvider: apply chatBackground wallpaper style to call embed
  container in full-view mode (not PiP) -- wallpapers carry over to calls
- useCallEmbed: pass themeKind through to CallEmbed constructor
- index.tsx: ignoreErrors: [Request timed out] to suppress matrixRTC
  heartbeat timeouts (REACT-9) from Sentry noise
- README: document 0.19.4, positioning fix, dark mode fix, wallpaper,
  millify Rolldown interop fix, Sentry noise filter

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/plugins/call/CallEmbed.ts

@@ -52,6 +52,8 @@ export class CallEmbed {
 
   private styleRetryObserver?: MutationObserver;
 
+  private themeKind: ElementCallThemeKind = 'dark';
+
   // Arrow-function class fields so dispose() passes the exact same reference to mx.off()
   private readonly boundOnEvent = (ev: MatrixEvent) => this.onEvent(ev);
 
@@ -175,6 +177,7 @@ export class CallEmbed {
     widget: Widget,
     container: HTMLElement,
     initialControlState?: CallControlState,
+    themeKind: ElementCallThemeKind = 'dark',
   ) {
     const iframe = CallEmbed.getIframe(
       widget.getCompleteUrl({ currentUserId: mx.getSafeUserId() }),
@@ -189,6 +192,7 @@ export class CallEmbed {
     this.room = room;
     this.iframe = iframe;
     this.container = container;
+    this.themeKind = themeKind;
 
     const controlState = initialControlState ?? new CallControlState(true, false, true);
     this.control = new CallControl(controlState, call, iframe);
@@ -218,9 +222,17 @@ export class CallEmbed {
   }
 
   public setTheme(theme: ElementCallThemeKind) {
-    return this.call.transport.send(WidgetApiToWidgetAction.ThemeChange, {
-      name: theme,
-    });
+    this.themeKind = theme;
+    const doc = this.document;
+    if (doc && this.joined) {
+      const styleEl = doc.getElementById('lotus-ec-styles');
+      if (styleEl) styleEl.textContent = this.buildStyleContent();
+    }
+    return this.call.transport
+      .send(WidgetApiToWidgetAction.ThemeChange, { name: theme })
+      .catch(() => {
+        // Widget transport not ready yet; theme URL param is the fallback
+      });
   }
 
   public hangup() {
@@ -304,22 +316,28 @@ export class CallEmbed {
     this.control.forceState(this.initialState);
   }
 
+  private buildStyleContent(): string {
+    return [
+      'html, body { background: none !important; }',
+      `:root { color-scheme: ${this.themeKind}; }`,
+      '[style*="height: 0"][style*="z-index: 1"][style*="align-self: center"] { display: none !important; }',
+    ].join('\n');
+  }
+
   private applyStyles(): void {
     const doc = this.document;
     if (!doc) return;
 
     doc.body.style.setProperty('background', 'none', 'important');
 
-    // Inject CSS for things that can't be reliably caught by DOM timing
     if (!doc.getElementById('lotus-ec-styles')) {
       const style = doc.createElement('style');
       style.id = 'lotus-ec-styles';
-      style.textContent = [
-        'body { background: none !important; }',
-        // Hide "using to Device key transport" status line
-        '[style*="height: 0"][style*="z-index: 1"][style*="align-self: center"] { display: none !important; }',
-      ].join('\n');
+      style.textContent = this.buildStyleContent();
       (doc.head ?? doc.body).appendChild(style);
+    } else {
+      const styleEl = doc.getElementById('lotus-ec-styles');
+      if (styleEl) styleEl.textContent = this.buildStyleContent();
     }
 
     // Hide EC built-in controls (we provide our own)