feat(composer): compose spoiler, annotation, and tooltip controls (#1491)

Signed-off-by: Taylor Ho <taylorkmho@gmail.com>
Co-authored-by: npub1223z34hd7vtwc6qj4s7flsxkj644nlre2nthu7lrrmkumhu3xddsrx9r6w <52a228d6edf316ec6812ac3c9fc0d696ab59fc7954d77e7be31eedcddf91335b@sprout-oss.stage.blox.sqprod.co>

desktop/src/shared/api/tauriMedia.ts

@@ -0,0 +1,16 @@
+import { invokeTauri } from "./tauri";
+
+/**
+ * Fetch relay media bytes over IPC (Rust reqwest, WARP-tunneled).
+ *
+ * Used by the composer image editor: wrapping the bytes in a same-origin
+ * `blob:` URL gives the canvas pixel access without CORS, so the media
+ * proxy needs no special headers. The Rust side enforces the same URL
+ * validation and size cap as the download commands.
+ */
+export async function fetchMediaBytes(
+  url: string,
+): Promise<Uint8Array<ArrayBuffer>> {
+  const bytes = await invokeTauri<number[]>("fetch_media_bytes", { url });
+  return new Uint8Array(bytes);
+}