fix(studio): a repair lands under the brush with no pill over it, and a browser with no device is not asked for one

docker/frontend/src/engine/inpaint.ts

@@ -71,16 +71,32 @@ async function warmsUp(ort: typeof Ort, session: Ort.InferenceSession): Promise<
   }
 }
 
+// Whether the browser has a device at all. `requestAdapter` answers for the
+// browser and not for this graph — an adapter is no promise the model runs on
+// it, the trial below is what settles that — but a *null* answer is a promise
+// it does not, and the attempt it saves is not nothing: a `create` that cannot
+// have a device still opens a session and tears it down (measured: 0.4s off the
+// first repair, and one backend fewer built on the way to the one that lasts).
+async function hasDevice(): Promise<boolean> {
+  try {
+    return Boolean(await navigator.gpu?.requestAdapter());
+  } catch {
+    return false;
+  }
+}
+
 // WebGPU first, the processor as the answer to every way that can fail: no
 // adapter, no `shader-f16` needed here but an op the provider never
 // implemented, a driver that opens a session and dies on the first dispatch.
 async function openSession(ort: typeof Ort): Promise<Ort.InferenceSession> {
-  try {
-    const gpu = await ort.InferenceSession.create(MODEL_URL, { executionProviders: ['webgpu'] });
-    if (await warmsUp(ort, gpu)) return gpu;
-    await gpu.release();
-  } catch {
-    // Whatever went wrong, the wasm provider is the fallback and not a failure.
+  if (await hasDevice()) {
+    try {
+      const gpu = await ort.InferenceSession.create(MODEL_URL, { executionProviders: ['webgpu'] });
+      if (await warmsUp(ort, gpu)) return gpu;
+      await gpu.release();
+    } catch {
+      // Whatever went wrong, the wasm provider is the fallback and not a failure.
+    }
   }
   return ort.InferenceSession.create(MODEL_URL, { executionProviders: ['wasm'] });
 }