[feat](trx-wefax): save images as YYYY-MM-DD_HH-MM-SS-freq_kHz_MODE.png

Include rig dial frequency and mode in WEFAX image filenames, matching
fldigi's approach of capturing tuning at save time. Images are saved to
~/.cache/trx-rs/wefax/. Server passes current rig state to the decoder
via set_tuning() before each processing block.

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

src/decoders/trx-wefax/src/decoder.rs

@@ -80,6 +80,10 @@ pub struct WefaxDecoder {
     signal_detect_count: u32,
     /// Accumulator for computing luminance variance within the current window.
     signal_detect_buf: Vec<f32>,
+    /// Current rig dial frequency in Hz (for image filenames).
+    freq_hz: u64,
+    /// Current rig mode name (for image filenames).
+    mode: String,
 }
 
 impl WefaxDecoder {
@@ -102,6 +106,8 @@ impl WefaxDecoder {
             sent_idle_event: false,
             signal_detect_count: 0,
             signal_detect_buf: Vec::with_capacity(INTERNAL_RATE as usize / 2),
+            freq_hz: 0,
+            mode: String::new(),
         }
     }
 
@@ -319,6 +325,12 @@ impl WefaxDecoder {
         events
     }
 
+    /// Update the current rig tuning (used for image filenames).
+    pub fn set_tuning(&mut self, freq_hz: u64, mode: &str) {
+        self.freq_hz = freq_hz;
+        self.mode = mode.to_string();
+    }
+
     /// Check if the decoder is currently receiving an image.
     pub fn is_receiving(&self) -> bool {
         matches!(
@@ -400,7 +412,7 @@ impl WefaxDecoder {
             // Save PNG if output directory is configured.
             if let Some(ref dir) = self.config.output_dir {
                 let output_path = PathBuf::from(dir);
-                match image.save_png(&output_path, ioc, lpm) {
+                match image.save_png(&output_path, self.freq_hz, &self.mode) {
                     Ok(p) => {
                         path_str = Some(p.to_string_lossy().into_owned());
                     }

src/decoders/trx-wefax/src/image.rs

@@ -43,8 +43,8 @@ impl ImageAssembler {
     pub fn save_png(
         &self,
         output_dir: &Path,
-        ioc: u16,
-        lpm: u16,
+        freq_hz: u64,
+        mode: &str,
     ) -> Result<PathBuf, String> {
         if self.lines.is_empty() {
             return Err("no image lines to save".into());
@@ -53,7 +53,7 @@ impl ImageAssembler {
         std::fs::create_dir_all(output_dir)
             .map_err(|e| format!("create output dir: {}", e))?;
 
-        let filename = generate_filename(ioc, lpm);
+        let filename = generate_filename(freq_hz, mode);
         let path = output_dir.join(&filename);
 
         let file = std::fs::File::create(&path)
@@ -89,7 +89,7 @@ impl ImageAssembler {
     }
 }
 
-fn generate_filename(ioc: u16, lpm: u16) -> String {
+fn generate_filename(freq_hz: u64, mode: &str) -> String {
     let now = std::time::SystemTime::now()
         .duration_since(std::time::UNIX_EPOCH)
         .unwrap_or_default();
@@ -97,10 +97,11 @@ fn generate_filename(ioc: u16, lpm: u16) -> String {
 
     // Convert to UTC datetime components manually (avoid chrono dependency).
     let (year, month, day, hour, min, sec) = unix_to_utc(secs);
+    let freq_khz = freq_hz / 1000;
 
     format!(
-        "WEFAX-{:04}-{:02}-{:02}T{:02}{:02}{:02}-IOC{}-{}lpm.png",
-        year, month, day, hour, min, sec, ioc, lpm
+        "{:04}-{:02}-{:02}_{:02}-{:02}-{:02}-{}_kHz_{}.png",
+        year, month, day, hour, min, sec, freq_khz, mode
     )
 }
 
@@ -179,7 +180,7 @@ mod tests {
         }
 
         let dir = std::env::temp_dir().join("trx-wefax-test");
-        let result = asm.save_png(&dir, 576, 120);
+        let result = asm.save_png(&dir, 7880000, "USB");
         assert!(result.is_ok(), "save_png failed: {:?}", result.err());
         let path = result.unwrap();
         assert!(path.exists());

src/trx-server/src/audio.rs

@@ -2780,6 +2780,13 @@ pub async fn run_wefax_decoder(
                         };
 
                         was_active = true;
+                        {
+                            let state = state_rx.borrow();
+                            decoder.set_tuning(
+                                state.status.freq.hz,
+                                &format!("{:?}", state.status.mode),
+                            );
+                        }
                         let events = tokio::task::block_in_place(|| {
                             let _span = info_span!("wefax_decode").entered();
                             decoder.process_samples(&mono)