refactor: 3-module pd architecture + viz non-blocking fix

- midi-in.pd: netreceive -> route -> unpack -> pitch/velocity outlets
- audio-out.pd: inlet~ -> dac~ abstraction
- synth.pd: consumer patch wiring midi-in -> voice -> audio-out
- led-matrix-viz.py: router socket non-blocking, registered with poller
- pd.rego: skip outlet/abstraction false positives in validation

pd/audio-out.pd

@@ -0,0 +1,5 @@
+#N canvas 0 0 200 100 10;
+#X obj 40 20 inlet~;
+#X obj 40 60 dac~;
+#X connect 0 0 1 0;
+#X connect 0 0 1 1;