feat(plugin): expose OrgSwitcher slot in extraRender

Add a single host-side mount point in extraRender.tsx:

    const OrgSwitcher = pluginManager?.components?.OrgSwitcher;
    ...
    {OrgSwitcher && <OrgSwitcher />}

A registered plugin can supply an Org switcher via
components.OrgSwitcher. When no plugin provides it, the host
renders nothing here, so the build is visually unchanged.

src/layouts/extraRender.tsx

@@ -120,6 +120,10 @@ export const ExtraContent = (props: { isDarkTheme?: boolean }) => {
 
   const { initialState } = initialInfo;
   const GlobalSettings = pluginManager?.components?.GlobalSettings;
+  // Plugin slot. A registered plugin can supply an Org switcher via
+  // components.OrgSwitcher; the host renders nothing when no plugin
+  // provides it.
+  const OrgSwitcher = pluginManager?.components?.OrgSwitcher;
   console.log('plugin+++++++++', pluginManager);
 
   const navigate = useNavigate();
@@ -271,6 +275,7 @@ export const ExtraContent = (props: { isDarkTheme?: boolean }) => {
   return (
     <Wrapper>
       {contextHolder}
+      {OrgSwitcher && <OrgSwitcher isDarkTheme={isDarkTheme} />}
       <div
         style={{
           display: 'flex',