feat: add skills, version pinning, CI/CD, and generated-file headers

- Create skills: rego-pd-validator, usb-gadget-configfs, led-matrix-msgpack-rpc
- Update pd-audio-synthesis skill with Uno Q specifics
- Add Pd version check (min 0.54.0) to start-synth.sh
- Add DO NOT EDIT headers to generated pd patches
- Add Gitea Actions CI workflow for patch validation
- Add ConditionPathExists guards to legacy systemd services
- Add 'just ci' recipe for CI

scripts/gen_mpk_sim.py

@@ -93,7 +93,10 @@ def gen():
         connect(c, msg, 0, ns, 0)
 
     # ── Write (Pd format: #X obj for objects, #X msg/text/floatatom/symbol for others) ──
-    lines = ["#N canvas 0 0 950 490 10;"]
+    lines = [
+        "#N canvas 0 0 950 490 10;",
+        "# DO NOT EDIT — generated by scripts/gen_mpk_sim.py;",
+    ]
     obj_types = {"bng","t","del","netsend","loadbang","hsl","comment"}
     for x, y, *args in o:
         etype = args[0]

scripts/gen_synth_pd.py

@@ -95,7 +95,10 @@ def gen():
     connect(c, panscale, 0, dac, 1)
 
     # ── Write ──
-    lines = ["#N canvas 0 0 900 550 10;"]
+    lines = [
+        "#N canvas 0 0 900 550 10;",
+        "# DO NOT EDIT — generated by scripts/gen_synth_pd.py;",
+    ]
     for x, y, t, *args in o:
         joined = " ".join(str(a) for a in args)
         lines.append(f"#X obj {x} {y} {joined};")

scripts/start-synth.sh

@@ -30,6 +30,14 @@ if ! command -v pd &>/dev/null; then
     die "Pure Data not found. Install: apt install puredata"
 fi
 
+MIN_PD_VERSION="0.54.0"
+PD_VERSION=$(pd --version 2>&1 | grep -oP '[\d]+\.[\d]+-?[\d]*' | head -1 || echo "0.0.0")
+if printf '%s\n' "$MIN_PD_VERSION" "$PD_VERSION" | sort -V | head -1 | grep -q "^$MIN_PD_VERSION$"; then
+    info "Pd version $PD_VERSION (>= $MIN_PD_VERSION)"
+else
+    die "Pd version $PD_VERSION is too old. Need >= $MIN_PD_VERSION"
+fi
+
 if [ ! -f "$PATCH" ]; then
     die "Patch not found: $PATCH"
 fi