[feat](trx-rs): add configurable noise blanker for SoapySDR backend

IQ-domain impulse noise blanker using exponential-smoothing RMS tracker. Samples exceeding threshold × running RMS are replaced with the last clean sample. Configurable via [sdr.noise_blanker] in TOML config and runtime via POST /set_sdr_noise_blanker API.

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

@@ -43,6 +43,7 @@ pub enum RigCommand {
     SetSdrLnaGain(f64),
     SetSdrAgc(bool),
     SetSdrSquelch { enabled: bool, threshold_db: f64 },
+    SetSdrNoiseBlanker { enabled: bool, threshold: f64 },
     SetWfmDeemphasis(u32),
     SetWfmStereo(bool),
     SetWfmDenoise(WfmDenoiseLevel),

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

@@ -525,6 +525,7 @@ pub fn command_from_rig_command(cmd: RigCommand) -> Box<dyn RigCommandHandler> {
         | RigCommand::SetSdrLnaGain(_)
         | RigCommand::SetSdrAgc(_)
         | RigCommand::SetSdrSquelch { .. }
+        | RigCommand::SetSdrNoiseBlanker { .. }
         | RigCommand::SetWfmDeemphasis(_)
         | RigCommand::SetWfmStereo(_)
         | RigCommand::SetWfmDenoise(_)

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

@@ -211,6 +211,17 @@ pub trait RigCat: Rig + Send {
         )))
     }
 
+    fn set_sdr_noise_blanker<'a>(
+        &'a mut self,
+        _enabled: bool,
+        _threshold: f64,
+    ) -> Pin<Box<dyn Future<Output = DynResult<()>> + Send + 'a>> {
+        Box::pin(std::future::ready(Err(
+            Box::new(response::RigError::not_supported("set_sdr_noise_blanker"))
+                as Box<dyn std::error::Error + Send + Sync>,
+        )))
+    }
+
     fn set_wfm_stereo<'a>(
         &'a mut self,
         _enabled: bool,

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

@@ -326,6 +326,10 @@ pub struct RigFilterState {
     pub sdr_squelch_enabled: Option<bool>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub sdr_squelch_threshold_db: Option<f64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub sdr_nb_enabled: Option<bool>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub sdr_nb_threshold: Option<f64>,
     #[serde(default = "default_wfm_deemphasis_us")]
     pub wfm_deemphasis_us: u32,
     #[serde(default = "default_wfm_stereo")]