fix: name the audio device in diagnostics instead of quoting its GUID

The watchdog fired exactly as intended and said:

  no audio at all from "{0.0.1.00000000}.{6a27abfd-f277-496b-b6f1-f92ec284c636}"

which tells the operator nothing they can act on. "DAX RX 1 (FlexRadio DAX)"
points straight at the DAX panel.

Endpoint ids are what gets CONFIGURED and stored, so they are what the recorder
holds; the friendly name is resolved only when something has gone wrong. When
the endpoint cannot be found at all the id is still shown — a device that has
disappeared explains an empty recording too.

internal/audio/wav.go

@@ -33,13 +33,13 @@ func writeWAV(path string, pcm []byte) error {
 	put(uint32(36 + dataLen))
 	f.WriteString("WAVE")
 	f.WriteString("fmt ")
-	put(uint32(16))               // PCM fmt chunk size
-	put(uint16(1))                // WAVE_FORMAT_PCM
-	put(uint16(channels))         //
-	put(uint32(sampleRate))       //
-	put(uint32(bytesPerSec))      // byte rate
-	put(uint16(blockAlign))       //
-	put(uint16(bitsPerSample))    //
+	put(uint32(16))            // PCM fmt chunk size
+	put(uint16(1))             // WAVE_FORMAT_PCM
+	put(uint16(channels))      //
+	put(uint32(sampleRate))    //
+	put(uint32(bytesPerSec))   // byte rate
+	put(uint16(blockAlign))    //
+	put(uint16(bitsPerSample)) //
 	f.WriteString("data")
 	put(uint32(dataLen))
 	_, err = f.Write(pcm)