[feat](trx-rs): add marine mode scaffolding and VDES fallback

Keep weak VDES bursts visible by emitting unsynced diagnostic frames instead of dropping them, remove receiver badges from FT8 and WSPR history rows, and carry the current MARINE composite-mode scaffolding through the shared mode enums and backend mappings.

Co-authored-by: OpenAI Codex <codex@openai.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

src/decoders/trx-vdes/src/lib.rs

@@ -33,6 +33,8 @@ const TER_MCS1_100_FEC_OUTPUT_BITS: usize = 1_872;
 const TER_MCS1_100_FEC_TAIL_BITS: usize = 10;
 const TER_MCS1_100_SYNC_BITS: &[u8; TER_MCS1_100_SYNC_SYMBOLS] = b"111111001101010000011001010";
 const PI4_QPSK_DIBITS: [u8; 4] = [0b00, 0b01, 0b11, 0b10];
+const MIN_SYNC_CANDIDATE_SCORE: f32 = 0.20;
+const MIN_SYNC_PARSE_SCORE: f32 = 0.50;
 
 #[derive(Debug, Clone)]
 pub struct VdesDecoder {
@@ -117,14 +119,32 @@ impl VdesDecoder {
         }
 
         let framed = extract_candidate_frame(&symbols)?;
-        let link_id = decode_link_id_from_symbols(&framed.symbols);
+        let rms = burst_rms(&samples);
+        let mode = classify_vdes_burst(framed.symbols.len());
         let payload_symbols = framed.payload_symbols();
         let deinterleaved = deinterleave_100khz_frame(payload_symbols);
+        if framed.sync_score < MIN_SYNC_PARSE_SCORE {
+            return Some(build_unsynced_message(
+                channel,
+                &framed,
+                &mode,
+                rms,
+                &deinterleaved,
+            ));
+        }
+
+        let link_id = decode_link_id_from_symbols(&framed.symbols);
         let (fec_input_symbols, fec_tail_symbols) = split_fec_frame(&deinterleaved);
         let coded_bits = dibits_to_bits(fec_input_symbols);
         let decoded_bits = viterbi_decode_rate_half(&coded_bits);
         if decoded_bits.is_empty() {
-            return None;
+            return Some(build_unsynced_message(
+                channel,
+                &framed,
+                &mode,
+                rms,
+                &deinterleaved,
+            ));
         }
         let parsed = parse_vdes_payload(&decoded_bits);
         let payload_bits = if parsed.payload_bits.is_empty() {
@@ -133,8 +153,6 @@ impl VdesDecoder {
             parsed.payload_bits.as_slice()
         };
         let raw_bytes = pack_bits_msb(payload_bits);
-        let rms = burst_rms(&samples);
-        let mode = classify_vdes_burst(framed.symbols.len());
         let link_text = link_id
             .map(|value| format!("LID {}", value))
             .unwrap_or_else(|| "LID ?".to_string());
@@ -308,7 +326,7 @@ fn extract_candidate_frame(symbols: &[u8]) -> Option<FrameSlice> {
             }
         }
     }
-    if best_score <= 0.5 {
+    if best_score <= MIN_SYNC_CANDIDATE_SCORE {
         return None;
     }
 
@@ -327,6 +345,53 @@ fn extract_candidate_frame(symbols: &[u8]) -> Option<FrameSlice> {
     })
 }
 
+fn build_unsynced_message(
+    channel: &str,
+    framed: &FrameSlice,
+    mode: &BurstMode<'_>,
+    rms: f32,
+    deinterleaved: &[u8],
+) -> VdesMessage {
+    let raw_bytes = pack_dibits_msb(deinterleaved);
+    let sync_pct = framed.sync_score * 100.0;
+    VdesMessage {
+        ts_ms: None,
+        channel: channel.to_string(),
+        message_type: mode.message_type,
+        repeat: 0,
+        mmsi: 0,
+        crc_ok: false,
+        bit_len: deinterleaved.len() * 2,
+        raw_bytes,
+        lat: None,
+        lon: None,
+        sog_knots: None,
+        cog_deg: None,
+        heading_deg: None,
+        nav_status: None,
+        vessel_name: Some(format!("Unsynced {} sym", framed.symbols.len())),
+        callsign: Some(format!("{} raw @{}", mode.label, framed.start_offset)),
+        destination: Some(format!(
+            "Weak sync {:.0}% ({}) · RMS {:.2} · raw symbol dump",
+            sync_pct, framed.sync_errors, rms
+        )),
+        message_label: Some("Unsynced".to_string()),
+        session_id: None,
+        source_id: None,
+        destination_id: None,
+        data_count: None,
+        asm_identifier: None,
+        ack_nack_mask: None,
+        channel_quality: None,
+        payload_preview: None,
+        link_id: None,
+        sync_score: Some(framed.sync_score),
+        sync_errors: Some(framed.sync_errors),
+        phase_rotation: Some(framed.phase_rotation),
+        fec_state: Some("Sync below parse threshold".to_string()),
+    }
+}
+
 fn syncword_score(symbols: &[u8], rotation: u8) -> (f32, u8) {
     if symbols.len() < TER_MCS1_100_SYNC_SYMBOLS {
         return (0.0, u8::MAX);