fix(tui): defer palette probe until first frame

packages/tui/src/app.tsx

@@ -285,8 +285,6 @@ export const run = Effect.fn("Tui.run")(function* (input: TuiInput) {
       )
       renderer.once("destroy", () => shutdown.openUnsafe())
       yield* Effect.tryPromise(async () => {
-        // Prewarm palette before ThemeProvider mounts so `system` theme avoids a first-paint fallback flash.
-        void renderer.getPalette({ size: 16 }).catch(() => undefined)
         const mode = handoff?.mode ?? (await renderer.waitForThemeMode(1000)) ?? "dark"
         if (renderer.isDestroyed) return
 

packages/tui/src/context/theme.tsx

@@ -184,11 +184,9 @@ const themeContext = createSimpleContext({
     }
 
     onMount(() => {
-      const systemTheme = resolveSystemTheme(store.mode)
-      void Promise.allSettled([
-        store.active === "system" ? systemTheme : Promise.resolve(),
-        syncCustomThemes(),
-      ]).finally(() => {
+      // Terminal palette queries serialize with frame output. Use the mode fallback for the first paint;
+      // App asks for the system palette after that frame and updates the theme in place.
+      void syncCustomThemes().finally(() => {
         valuesV2()
         setStore("ready", true)
       })