[feat](trx-rs): expose WFM stereo denoise toggle in UI

Wire the StereoDenoise processor through the full stack:
- Add SetWfmDenoise command variant and RigCat trait method (trx-core)
- Add wfm_denoise field to RigFilterState with default true
- Add protocol command and bidirectional mapping (trx-protocol)
- Add rig_task command handler (trx-server)
- Implement set_wfm_denoise in SoapySdrRig backend
- Add /set_wfm_denoise API endpoint (trx-frontend-http)
- Add denoise checkbox in WFM controls with SSE sync and
  localStorage persistence

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-core/src/rig/command.rs

@@ -36,5 +36,6 @@ pub enum RigCommand {
     SetSdrGain(f64),
     SetWfmDeemphasis(u32),
     SetWfmStereo(bool),
+    SetWfmDenoise(bool),
     GetSpectrum,
 }

src/trx-core/src/rig/controller/handlers.rs

@@ -519,6 +519,7 @@ pub fn command_from_rig_command(cmd: RigCommand) -> Box<dyn RigCommandHandler> {
         | RigCommand::SetSdrGain(_)
         | RigCommand::SetWfmDeemphasis(_)
         | RigCommand::SetWfmStereo(_)
+        | RigCommand::SetWfmDenoise(_)
         | RigCommand::GetSpectrum => Box::new(GetSnapshotCommand),
     }
 }

src/trx-core/src/rig/mod.rs

@@ -185,6 +185,16 @@ pub trait RigCat: Rig + Send {
         )))
     }
 
+    fn set_wfm_denoise<'a>(
+        &'a mut self,
+        _enabled: bool,
+    ) -> Pin<Box<dyn Future<Output = DynResult<()>> + Send + 'a>> {
+        Box::pin(std::future::ready(Err(
+            Box::new(response::RigError::not_supported("set_wfm_denoise"))
+                as Box<dyn std::error::Error + Send + Sync>,
+        )))
+    }
+
     /// Return the current filter state if this backend supports filter controls.
     fn filter_state(&self) -> Option<state::RigFilterState> {
         None

src/trx-core/src/rig/state.rs

@@ -277,6 +277,8 @@ pub struct RigFilterState {
     pub wfm_stereo: bool,
     #[serde(default)]
     pub wfm_stereo_detected: bool,
+    #[serde(default = "default_wfm_denoise")]
+    pub wfm_denoise: bool,
 }
 
 fn default_wfm_deemphasis_us() -> u32 {
@@ -287,6 +289,10 @@ fn default_wfm_stereo() -> bool {
     true
 }
 
+fn default_wfm_denoise() -> bool {
+    true
+}
+
 /// Spectrum data from SDR backends (FFT magnitude over the full capture bandwidth).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct SpectrumData {