Add bias_t parameter to SDR command builders

The bias_t parameter was being passed to build_fm_demod_command()
but wasn't defined in the method signatures, causing an unexpected
keyword argument error.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

utils/sdr/hackrf.py

@@ -60,7 +60,8 @@ class HackRFCommandBuilder(CommandBuilder):
         gain: Optional[float] = None,
         ppm: Optional[int] = None,
         modulation: str = "fm",
-        squelch: Optional[int] = None
+        squelch: Optional[int] = None,
+        bias_t: bool = False
     ) -> list[str]:
         """
         Build SoapySDR rx_fm command for FM demodulation.
@@ -84,6 +85,9 @@ class HackRFCommandBuilder(CommandBuilder):
         if squelch is not None and squelch > 0:
             cmd.extend(['-l', str(squelch)])
 
+        if bias_t:
+            cmd.extend(['-T'])
+
         # Output to stdout
         cmd.append('-')