P25 conventional decode mode + conventional-channel attribution (node-26#24, #20)

op25-container
- generate-config takes p25_mode "conventional" + conv_channels [{frequency,
  name, nac}]. It builds fixed fsk4 channels (up to 2 on one non-tunable SDR,
  DC spike kept off the channels) with no control channel to hunt. Two
  channels send audio to UDP 23456/23457, and audio.py -2 + amplify(2) keeps
  levels.
- tk_drb_conv.py (a tk_p25.rx_ctl subclass, copied into OP25 apps) reports
  voice / NAC / encryption (LC service options + LDU2 ESS algid/keyid) for
  conventional channels and applies the per-channel NAC filter, which stock
  tk_p25 does not. Analog uses it too.
- Trunked P25 config is unchanged when p25_mode is absent.

drb-edge-node
- radio_config: system kind from type + config.mode (missing = trunked).
- conventional.py normalizes the console: a distinctive LC TGID, else the
  channel's last TGID (30 s), else a synthetic per-channel id (freq/100 Hz).
  Encrypted rows are never talkers. With exactly one conventional channel,
  orphan audio is attributed to it at close, which fixes analog recording
  (#20). The synthetic id and the real TGID on one channel never split.
- Health/dashboard: P25 conventional listen tab (/api/listen p25conv), and
  conventional decode + encryption checks. The checkin carries radio_channels.
- Tests: edge 296 pass; op25-container 18 (new CI job). Reviewed by
  drb-audio-review (findings fixed; simultaneous two-channel mixdown filed
  as #26) and drb-qa-review.

Not verified on SDR hardware.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

op25-container/app/internal/liquidsoap_config_utils.py

@@ -2,7 +2,26 @@ import os
 from internal.op25_liq_template import liquidsoap_config_template
 from models import IcecastConfig
 
-def generate_liquid_script(config: IcecastConfig):
+# P25 conventional with two channels (node-26#24): OP25 sends channel A's
+# audio to UDP 23456 and channel B's to 23457, and audio.py -2 puts them on the
+# left and right of the stereo stream. Every output below is mean(input) — mono
+# — so a lone talker on one side would come out 6 dB down; doubling first keeps
+# the common case (one channel keyed) at the same level as single-channel mode.
+# Liquidsoap mixes in float, so the doubling cannot clip before the output.
+_TWO_CHANNEL_AUDIO_ARGS = " -2"
+_TWO_CHANNEL_MIX = "input = amplify(2.0, input)  # two conventional channels, L=A R=B"
+
+
+def render_liquid_script(config: IcecastConfig, two_channel: bool = False) -> str:
+    content = liquidsoap_config_template
+    for key, value in config.model_dump().items():
+        content = content.replace(f"${{{key}}}", str(value))
+    content = content.replace("${audio_py_args}", _TWO_CHANNEL_AUDIO_ARGS if two_channel else "")
+    content = content.replace("${two_channel_mix}", _TWO_CHANNEL_MIX if two_channel else "")
+    return content
+
+
+def generate_liquid_script(config: IcecastConfig, two_channel: bool = False):
     """
     Generates the "*.liq" file that's run by OP25 on startup. 
 
@@ -13,13 +32,7 @@ def generate_liquid_script(config: IcecastConfig):
                           Keys should match the variable names in the template (e.g., 'icecast_host').
     """
     try:
-        content = liquidsoap_config_template
-        # Replace variables
-        for key, value in config.model_dump().items():
-            placeholder = f"${{{key}}}"
-            # Ensure the value is converted to string for replacement
-            content = content.replace(placeholder, str(value))
-            print(f"  - Replaced placeholder {placeholder}")
+        content = render_liquid_script(config, two_channel)
 
         # Write the processed content to the output path
         output_path = "/configs/op25.liq"