Offer three denoise networks and a method to choose between them

AI Denoise's Apply switch becomes Method: Bilinear, Fast, Medium, Best,
default Best, so an untouched raw writes nothing and develops through the
mixture. `apply` is still read and never written: 0 is Bilinear, 1 keeps
a network already chosen.

- Best is the mixture of a flat and an edge expert with a learned gate;
  Medium and Fast are students distilled from it. 2.48 s, 0.79 s and
  0.57 s for a 20 MP frame on TensorRT fp16.
- Each network carries its own tile border (256 for the mixture, 192 for
  the students) through `dr_denoise::Shipped` and `TileNet::halo`.
- The file is hashed once at open and each network keys its own cached
  result; Bilinear keeps the result in memory for the way back.
- Each has an .a16w16 sibling for the Hexagon: 0.00 dB on the 6D gate,
  at most 0.11 dB with the noise scaled x0.5 to x4.
- APK BUNDLED 19 -> 23; the PKGBUILD installs all three.

ui/dr-ui/src/library/paths.rs

@@ -390,13 +390,28 @@ pub fn inpaint_model() -> Option<PathBuf> {
 }
 
 /// TRACES: FR-DEV-3g
-/// The learned demosaic and denoise, as shipped in `models/denoise/`.
-pub const DENOISE_MODEL: &str = "mosaic-1408.onnx";
+/// The network a denoise method runs, as shipped in `models/denoise/`;
+/// `None` for the classical demosaic, which runs none.
+pub fn denoise_network(
+    method: dr_pipeline::learned_denoise::Method,
+) -> Option<dr_denoise::Shipped> {
+    use dr_pipeline::learned_denoise::Method;
+    match method {
+        Method::Bilinear => None,
+        Method::Fast => Some(dr_denoise::FAST),
+        Method::Medium => Some(dr_denoise::MEDIUM),
+        Method::Best => Some(dr_denoise::BEST),
+    }
+}
 
 /// TRACES: FR-DEV-3g
-/// Where the denoise model is, by the border filler's search.
-pub fn denoise_model() -> Option<PathBuf> {
-    shared_model(DENOISE_MODEL)
+/// Where a method's network is, by the border filler's search, and the
+/// context it needs.
+pub fn denoise_model(
+    method: dr_pipeline::learned_denoise::Method,
+) -> Option<(PathBuf, dr_denoise::Shipped)> {
+    let net = denoise_network(method)?;
+    Some((shared_model(net.file)?, net))
 }
 
 #[cfg(test)]