fix: sync context panel iframe themes

Keeps embedded sessions aligned with parent theme
Prevents iframe reloads on theme changes
Supports theme hotkeys from focused iframes

packages/ui/src/contexts/theme-sync-payload.ts

@@ -0,0 +1,14 @@
+import type { Theme } from '@/types/theme';
+import { isValidTheme } from './theme-validation';
+
+export type ThemeSyncPayloadShape = {
+  currentTheme?: unknown;
+};
+
+export const getSyncedThemeFromPayload = (payload: ThemeSyncPayloadShape): Theme | null => (
+  isValidTheme(payload.currentTheme) ? payload.currentTheme : null
+);
+
+export const getSyncedThemeVariant = (payload: ThemeSyncPayloadShape): 'light' | 'dark' | null => (
+  getSyncedThemeFromPayload(payload)?.metadata.variant ?? null
+);