[feat](trx-core): add SetSdrLnaGain command and sdr_lna_gain_db state

Add RigCommand::SetSdrLnaGain(f64), the corresponding default RigCat
trait method set_sdr_lna_gain, and an sdr_lna_gain_db: Option<f64>
field to RigFilterState for backends that expose a named LNA gain
element.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

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

@@ -41,6 +41,7 @@ pub enum RigCommand {
     SetBandwidth(u32),
     SetFirTaps(u32),
     SetSdrGain(f64),
+    SetSdrLnaGain(f64),
     SetSdrAgc(bool),
     SetSdrSquelch { enabled: bool, threshold_db: f64 },
     SetWfmDeemphasis(u32),

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

@@ -523,6 +523,7 @@ pub fn command_from_rig_command(cmd: RigCommand) -> Box<dyn RigCommandHandler> {
         | RigCommand::SetBandwidth(_)
         | RigCommand::SetFirTaps(_)
         | RigCommand::SetSdrGain(_)
+        | RigCommand::SetSdrLnaGain(_)
         | RigCommand::SetSdrAgc(_)
         | RigCommand::SetSdrSquelch { .. }
         | RigCommand::SetWfmDeemphasis(_)

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

@@ -190,6 +190,16 @@ pub trait RigCat: Rig + Send {
         )))
     }
 
+    fn set_sdr_lna_gain<'a>(
+        &'a mut self,
+        _gain_db: f64,
+    ) -> Pin<Box<dyn Future<Output = DynResult<()>> + Send + 'a>> {
+        Box::pin(std::future::ready(Err(
+            Box::new(response::RigError::not_supported("set_sdr_lna_gain"))
+                as Box<dyn std::error::Error + Send + Sync>,
+        )))
+    }
+
     fn set_sdr_agc<'a>(
         &'a mut self,
         _enabled: bool,

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

@@ -313,6 +313,8 @@ pub struct RigFilterState {
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub sdr_gain_db: Option<f64>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub sdr_lna_gain_db: Option<f64>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub sdr_agc_enabled: Option<bool>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub sdr_squelch_enabled: Option<bool>,