Run each model on the Hexagon in the form measured to hold it

The engine knew f32 and int8, and gave the Hexagon int8 for every role it
served. Measured on the tablet itself (inference.md §1.5), int8 lost
5% of the detector's faces at 40-80 px, moved the landmarks 1.5 px,
emptied the segmenter's scores and cost the denoiser 5-9 dB; fp16 the HTP
refuses outright. `Form` gains A16W8 and A16W16, and `Rung::form` now
names one per role: detectors and landmarks A16W8, the segmenter, scene
model, border filler and denoiser A16W16, XFeat int8. The embedder and
the eye classifiers stay on the CPU.

Each loader resolves its `<stem>.<form>.onnx` sibling; the segmenter and
XFeat, compiled into the binary, embed their quantised forms on Android
only and pick through `choose_embedded`. The probe, the compile step and
the cache fingerprint follow the form instead of assuming int8. Detectors
on the new form write `scrfd_*_a16+w600k_mbf`, and `model_ids` answers
for all three spellings.

On the tablet (ORT 1.29 + QNN 2.42), each shipped file against f32 on the
same inputs, and against the CPU's f32 time:
  SCRFD 500m/2.5g/10g  A16W8   100% of faces in every band   4.2/5.1/9.0 ms vs 17/56/198
  landmarks            A16W8   0.25 px in the 192 crop        0.5 ms vs 2.8
  YOLO26n-seg          A16W16  98.2% found, mask IoU 0.994    12.9 ms vs 90
  scene model          A16W16  98.9% of cells agree           15 ms vs 151
  MI-GAN               A16W16  41 dB from f32 in the fill     87 ms vs 488
  XFeat                int8    pano alignment 0.45 px (f32's own spread 0.41)  6.5 ms vs 58
  denoiser             A16W16  0.00 dB at every ISO            95 ms vs 1510 a tile
Face numbers are over public COCO val2017 photographs, not a library.

The APK carries the siblings (BUNDLED 15 -> 19; the old int8 detectors
removed), about 43 MB more. The Windows installer and its CI count skip
them; the Arch and Flatpak packages list their files and never had them.
The ladder example takes a role per model, which is how the per-role
forms above were seen landing on the NPU from the real probe.

core/dr-face/src/detect.rs

@@ -137,8 +137,8 @@ impl Detection {
 /// A loaded SCRFD graph.
 pub struct Detector {
     session: Model,
-    /// f32 or int8 — the int8 form finds a different set of faces and is a
-    /// different detector in `model_id` (docs/dev/inference.md §7).
+    /// f32 or a quantised form — which finds a different set of faces and is
+    /// a different detector in `model_id` (docs/dev/inference.md §7).
     form: Form,
     /// Feature-map count: 3 for strides {8,16,32}, 4 for {8,16,32,64}.
     ///
@@ -155,7 +155,7 @@ impl Detector {
     }
 
     /// Load the canonical f32 file at `path`, or the form the device's
-    /// backend wants instead — the `.int8.onnx` beside it on a Hexagon —
+    /// backend wants instead — the `.a16w8.onnx` beside it on a Hexagon —
     /// which [`Detector::form`] then reports.
     pub fn from_path(path: impl AsRef<std::path::Path>) -> Result<Self, FaceError> {
         let (path, form) = dr_inference_engine::resolve_model(Role::Detector, path.as_ref());

core/dr-face/src/landmarks.rs

@@ -123,13 +123,22 @@ pub struct Landmarker {
 }
 
 impl Landmarker {
+    /// The graph at `path`, or the `.a16w8.onnx` sibling beside it when the
+    /// device's backend runs that (the Hexagon, inference.md §1.5: 0.25 px
+    /// from f32 in the 192 crop, where int8 moved the points by 1.5).
     pub fn from_path(path: impl AsRef<std::path::Path>) -> Result<Self, FaceError> {
+        let (path, form) = dr_inference_engine::resolve_model(Role::Landmarks, path.as_ref());
         let bytes = std::fs::read(path).map_err(FaceError::ModelRead)?;
-        Self::from_bytes(&bytes)
+        Self::from_bytes_in(&bytes, form)
     }
 
     pub fn from_bytes(bytes: &[u8]) -> Result<Self, FaceError> {
-        let model = dr_inference_engine::open(Role::Landmarks, Form::F32, bytes)?;
+        Self::from_bytes_in(bytes, Form::F32)
+    }
+
+    /// `bytes` in a stated numeric form; the output keeps its meaning.
+    pub fn from_bytes_in(bytes: &[u8], form: Form) -> Result<Self, FaceError> {
+        let model = dr_inference_engine::open(Role::Landmarks, form, bytes)?;
         let acquired = model.acquire()?;
         let session = acquired.lock();