Phase 1-4: Audio stack, mixer engine, MIDI, and network API

P2-R1: ALSA + JACK2 low-latency config (scripts, quirks, tuning)
P2-R2: Carla integration (build scripts, 8ch rack config, NAM LV2 support)
P2-R3: Plugin manager, categories, blacklist, NAM model support
P3-R1: Mixer DSP engine (channel strip, routing matrix, bus mgr, automation)
P4-R1: MIDI engine (learn mode, clock sync, HID discovery, mapping store)
P4-R2: Network API (OSC server, FastAPI REST, WebSocket, auth, rate limiter)
P5-R1: Touchscreen UI evaluation + main entry point
docs: Audio stack, Carla integration, MIDI support, UI evaluation
tests: Full test suite (292 passing)

scripts/jack-route-default

@@ -0,0 +1,40 @@
+#!/bin/bash
+# jack-route-default — auto-connect JACK system captures to playbacks
+# Run after JACK is started. Creates a 1:1 through-patch for direct monitoring.
+
+jack_wait -w
+
+# Get available ports
+captures=$(jack_lsp -c system | grep capture || true)
+playbacks=$(jack_lsp -c system | grep playback || true)
+
+if [ -z "$captures" ] || [ -z "$playbacks" ]; then
+    echo "No system capture or playback ports found. Is JACK running?"
+    echo "Check: jack_lsp -c system"
+    exit 1
+fi
+
+# Route capture -> playback in pairs
+# Assumes matching channel counts; pairs capture_1->playback_1, etc.
+MAX_CHANNELS=18
+
+for i in $(seq 1 $MAX_CHANNELS); do
+    CAP_PORT="system:capture_${i}"
+    PB_PORT="system:playback_${i}"
+
+    if jack_lsp -c system | grep -q "^${CAP_PORT}$" && \
+       jack_lsp -c system | grep -q "^${PB_PORT}$"; then
+        jack_connect "$CAP_PORT" "$PB_PORT" 2>/dev/null && \
+            echo "  Connected: $CAP_PORT -> $PB_PORT" || \
+            echo "  Already connected: $CAP_PORT -> $PB_PORT"
+    fi
+done
+
+# Optional: start a2jmidid for MIDI bridging
+if command -v a2j_control &> /dev/null; then
+    if ! pgrep -x a2jmidid > /dev/null; then
+        a2j_control start 2>/dev/null && echo "  MIDI bridge (a2jmidid) started"
+    fi
+fi
+
+echo "Routing complete."