fix(electron): theme Windows titlebar overlay (#16843)

Co-authored-by: Brendan Allan <brendonovich@outlook.com>

packages/app/src/app.tsx

@@ -62,6 +62,9 @@ declare global {
       deepLinks?: string[]
       wsl?: boolean
     }
+    api?: {
+      setTitlebar?: (theme: { mode: "light" | "dark" }) => Promise<void>
+    }
   }
 }
 
@@ -115,7 +118,11 @@ export function AppBaseProviders(props: ParentProps) {
   return (
     <MetaProvider>
       <Font />
-      <ThemeProvider>
+      <ThemeProvider
+        onThemeApplied={(_, mode) => {
+          void window.api?.setTitlebar?.({ mode })
+        }}
+      >
         <LanguageProvider>
           <UiI18nBridge>
             <ErrorBoundary fallback={(error) => <ErrorPage error={error} />}>

packages/app/src/components/titlebar.tsx

@@ -1,4 +1,4 @@
-import { createEffect, createMemo, Show, untrack } from "solid-js"
+import { createEffect, createMemo, onCleanup, Show, untrack } from "solid-js"
 import { createStore } from "solid-js/store"
 import { useLocation, useNavigate, useParams } from "@solidjs/router"
 import { IconButton } from "@opencode-ai/ui/icon-button"
@@ -282,7 +282,7 @@ export function Titlebar() {
       >
         <div id="opencode-titlebar-right" class="flex items-center gap-1 shrink-0 justify-end" />
         <Show when={windows()}>
-          <div class="w-6 shrink-0" />
+          {!tauriApi() && <div class="w-36 shrink-0" />}
           <div data-tauri-decorum-tb class="flex flex-row" />
         </Show>
       </div>