feat: Add new emoji assets and an UpdateBanner component.

packages/platform-web/src/idle.js

@@ -0,0 +1,36 @@
+/**
+ * Web platform idle detection using Page Visibility API.
+ * Provides a simplified version of the Electron idle API.
+ */
+let idleCallback = null;
+let lastActiveTime = Date.now();
+
+function handleVisibilityChange() {
+  if (!idleCallback) return;
+  if (document.hidden) {
+    idleCallback({ isIdle: true });
+  } else {
+    lastActiveTime = Date.now();
+    idleCallback({ isIdle: false });
+  }
+}
+
+export default {
+  getSystemIdleTime() {
+    // Return seconds since last activity (approximation using visibility)
+    if (document.hidden) {
+      return Math.floor((Date.now() - lastActiveTime) / 1000);
+    }
+    return 0;
+  },
+
+  onIdleStateChanged(callback) {
+    idleCallback = callback;
+    document.addEventListener('visibilitychange', handleVisibilityChange);
+  },
+
+  removeIdleStateListener() {
+    idleCallback = null;
+    document.removeEventListener('visibilitychange', handleVisibilityChange);
+  },
+};