Move the panorama keypoint detector onto the engine, and probe with a detector

XFeat's two exports are a Keypoints role now; the crate no longer names
tract, and the app compiles TensorRT engines for both ahead of the
first merge. The probe picks the smallest *detector* rather than the
smallest file: the tablet's first run chose the 112 KB eye classifier,
which has no int8 form, and reported the Hexagon as failed for want of
one.

apps/darkroom-android/src/lib.rs

@@ -335,9 +335,15 @@ fn unpack_bundled_models(app: &slint::android::AndroidApp) {
     // chose that rung and ignores it otherwise.
     const BUNDLED: [(&std::ffi::CStr, &str); 13] = [
         (c"models/scrfd_500m_640.onnx", "scrfd_500m_640.onnx"),
-        (c"models/scrfd_500m_640.int8.onnx", "scrfd_500m_640.int8.onnx"),
+        (
+            c"models/scrfd_500m_640.int8.onnx",
+            "scrfd_500m_640.int8.onnx",
+        ),
         (c"models/scrfd_2.5g_640.onnx", "scrfd_2.5g_640.onnx"),
-        (c"models/scrfd_2.5g_640.int8.onnx", "scrfd_2.5g_640.int8.onnx"),
+        (
+            c"models/scrfd_2.5g_640.int8.onnx",
+            "scrfd_2.5g_640.int8.onnx",
+        ),
         (c"models/scrfd_10g_640.onnx", "scrfd_10g_640.onnx"),
         (c"models/scrfd_10g_640.int8.onnx", "scrfd_10g_640.int8.onnx"),
         (c"models/arcface_mbf_b1.onnx", "arcface_mbf_b1.onnx"),