fix(FR-3834): seed the Branding draft from the saved domain document

The editor draft (and so the JSON modal) was always seeded from the
shipped theme.json, even when the domain had an applied document. The
domain getter existed and was tested but the editor never read it. Seed
from the domain document first, then theme.json — what the Branding
comment and the PR already described. Reset still restores the shipped
values.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ByYKF612aRtRCXZWfExDuf

Author: ironAiken2

react/src/hooks/useDefaultTheme.ts

@@ -5,6 +5,7 @@
 import { App } from '../app-shim';
 import {
   APPEARANCE_SCHEMA_VERSION,
+  getDomainAppearanceConfig,
   getStaticAppearanceConfig,
 } from '../helper/customThemeConfig';
 import { useBAISettingUserState } from './useBAISetting';
@@ -30,20 +31,19 @@ export const useDefaultTheme = () => {
     'custom_theme_config',
   );
 
-  // Seed the draft from the SHIPPED document (never from `rawThemeConfig`:
-  // in preview mode that IS the draft, so reseeding from it would loop). A
-  // draft from before the v2 format (no schemaVersion) is reseeded rather
-  // than edited — its v1 paths no longer mean anything to the editor.
-  // Note: useBAISettingUserState returns null (not undefined) when
-  // localStorage has no value.
+  // Seed the draft from the saved domain document, else the SHIPPED one —
+  // never from `rawThemeConfig`, which in preview mode IS the draft and would
+  // loop. A draft from before the v2 format (no schemaVersion) is reseeded
+  // rather than edited. Note: useBAISettingUserState returns null (not
+  // undefined) when localStorage has no value.
   const initializeDefaultTheme = useEffectEvent(() => {
-    const shipped = getStaticAppearanceConfig();
+    const seed = getDomainAppearanceConfig() ?? getStaticAppearanceConfig();
     if (
       (_.isNil(defaultTheme) ||
         defaultTheme.schemaVersion !== APPEARANCE_SCHEMA_VERSION) &&
-      !_.isNil(shipped)
+      !_.isNil(seed)
     ) {
-      setDefaultTheme(_.cloneDeep(shipped));
+      setDefaultTheme(_.cloneDeep(seed));
     }
   });
   useEffect(() => {