Start the inference engine from both apps and show its choice in Settings

The desktop names where a package may have put libonnxruntime — an
override variable, beside the executable, the package's own library
directory, the Flatpak prefix, the system library directory — and
Android points at the APK's native library directory, which is also
what Qualcomm's DSP loader must be told for the Hexagon skel. Android
starts the engine at the end of the model unpack rather than at launch,
because the probe fingerprints the model files and a first launch has
none until then.

The About panel gains an Inference row beside Graphics, re-read every
two seconds while the probe runs and engines land, and faces.model_id
carries the detector's form: an int8 detector finds a different set of
faces and is a different population (docs/inference.md §7). A
low-memory signal drops every idle session with the GPU caches.

The APK assembly bundles ONNX Runtime and the Qualcomm HTP libraries
from Maven, fetched by tools/fetch-android-runtime.sh with their
published checksums; RUNTIME_DIR=none builds the tract-only APK, which
is a slower app and not a broken one. The desktop packages carry no
runtime yet.

Two probe fixes from the first desktop run: the floor must not be
built with CPU fallback disabled, and a versioned libonnxruntime.so is
a runtime too. On the reference desktop the probe now loads ONNX
Runtime 1.30, measures 30 ms on the CPU provider, and selects TensorRT
at 1.5 ms.

ui/dr-ui/src/lib.rs

@@ -39,6 +39,7 @@ pub mod identity;
 mod identity_ui;
 mod import;
 mod import_ui;
+pub mod inference;
 mod labels;
 mod library;
 mod library_ui;
@@ -1209,6 +1210,32 @@ pub fn run(paths: Vec<PathBuf>) -> Result<()> {
         None => window.set_backend("NO GPU".into()),
     }
 
+    // TRACES: FR-INF-1
+    // What the models run on. Re-read every two seconds because the answer
+    // changes twice after launch — when the probe reports and as each
+    // engine lands — and the page is open for longer than either takes.
+    {
+        let set = |w: &AppWindow| {
+            let (line, detail) = inference::about_lines();
+            w.set_inference_backend(line.into());
+            w.set_inference_detail(detail.into());
+        };
+        set(&window);
+        let weak = window.as_weak();
+        let timer = Rc::new(slint::Timer::default());
+        let held = timer.clone();
+        timer.start(
+            slint::TimerMode::Repeated,
+            std::time::Duration::from_secs(2),
+            move || {
+                let _keep = &held;
+                if let Some(w) = weak.upgrade() {
+                    set(&w);
+                }
+            },
+        );
+    }
+
     // TRACES: NFR-OPS-1
     // The diagnostics bundle, wired as the two presses the requirement
     // describes. Preparing gathers the log and the crash records into memory
@@ -1638,7 +1665,7 @@ pub fn run(paths: Vec<PathBuf>) -> Result<()> {
             library.set_fetch_ahead(stored.cache.fetch_ahead);
             library.set_write_xmp_sidecars(stored.library.write_xmp_sidecars);
             library.set_timeline_bars(stored.library.timeline_bars);
-            library.set_face_model_id(stored.faces.detector.model_id());
+            library.set_face_model_id(inference::model_id(stored.faces.detector));
         }
 
         // --- the export folder picker ----------------------------------------
@@ -1790,7 +1817,7 @@ pub fn run(paths: Vec<PathBuf>) -> Result<()> {
                 // file is installed, and how much of the library that
                 // pipeline has covered — which for a freshly chosen one is
                 // nothing, and saying so is the point.
-                lib.set_face_model_id(s.faces.detector.model_id());
+                lib.set_face_model_id(inference::model_id(s.faces.detector));
                 if let Some(w) = weak.upgrade() {
                     refresh_face_status(&w, &lib, s.faces.detector);
                 }
@@ -3933,7 +3960,7 @@ fn refresh_face_status(
         window,
         &library.catalog(),
         store.as_ref(),
-        detector.model_id(),
+        inference::model_id(detector),
         models.as_ref().is_some_and(|m| m.eyes.is_some()),
     );
     window.set_identity_model_missing(models.is_none());