Initial commit: Arduino Uno Q USB Audio Synth project

- USB gadget (UAC1 + MIDI) with boot persistence
- USB host mode with auto-detection
- Pure Data synth patch with ALSA + UDP netreceive MIDI input
- MIDI rawmidi-to-UDP bridge (midi-bridge.py)
- LED matrix visualization (led-matrix-viz.py via arduino-router RPC)
- MCU sketch for LED matrix control (Arduino_RouterBridge + ArduinoGraphics)
- Conftest/OPA Rego policy validation suite for .pd files
- gen_synth_pd.py: programmatic .pd file generator
- System services: midi-bridge, led-matrix-viz, pd-synth-auto, usb-role-detect
- Justfile with deploy, enable, diagnostic recipes
- Diagnostic script (diag.sh)

system/asound.conf

@@ -0,0 +1,44 @@
+# ALSA configuration for USB gadget audio
+# The UAC1 gadget appears as a ALSA card (typically card 1 or 2).
+# This config routes Pd audio output to the USB gadget.
+
+# Default PCM device for USB gadget audio
+pcm.!default {
+    type plug
+    slave {
+        pcm "hw:UAC1Gadget,0"
+        format S16_LE
+        channels 2
+        rate 48000
+    }
+}
+
+# Control device
+ctl.!default {
+    type hw
+    card UAC1Gadget
+}
+
+# Software volume control via ALSA (hardware may not have mixer)
+pcm.softvol {
+    type softvol
+    slave.pcm "hw:UAC1Gadget,0"
+    control {
+        name "Master Playback Volume"
+        card UAC1Gadget
+    }
+    min_dB -51.0
+    max_dB 0.0
+    resolution 256
+}
+
+# Null sink for testing when no USB gadget is connected
+pcm.loopback {
+    type plug
+    slave {
+        pcm "hw:Loopback,0,0"
+        format S16_LE
+        channels 2
+        rate 48000
+    }
+}