fix(arduino): guard desktop-only synth TUs; library.json build filter

library.json

@@ -0,0 +1,16 @@
+{
+  "name": "ModuLisp",
+  "version": "0.2.0",
+  "description": "ModuLisp live-coding signal engine extracted from uSEQ (external input/sink/command registries)",
+  "keywords": "signal-engine, live-coding, dsp",
+  "license": "MPL-2.0",
+  "platforms": ["rp2040"],
+  "frameworks": ["arduino"],
+  "build": {
+    "srcFilter": [
+      "+<*>",
+      "-<signal_engine/synth_graph.cpp>",
+      "-<signal_engine/synth_registry.cpp>"
+    ]
+  }
+}

src/signal_engine/synth_graph.cpp

@@ -1,3 +1,9 @@
+
+
+// Desktop/WASM-only domain (build_profile.h: USEQ_HAS_SYNTH_ENGINE is
+// 0 under ARDUINO); the firmware profile must not compile these TUs.
+#if !defined(ARDUINO)
+
 #include "synth_graph.h"
 #include "cold_eval.h"
 #include <cstring>
@@ -206,3 +212,6 @@ const char* synth_artifacts_json(const SignalEngine& engine) {
 }
 
 } // namespace sig
+
+
+#endif  // !defined(ARDUINO)

src/signal_engine/synth_registry.cpp

@@ -1,3 +1,9 @@
+
+
+// Desktop/WASM-only domain (build_profile.h: USEQ_HAS_SYNTH_ENGINE is
+// 0 under ARDUINO); the firmware profile must not compile these TUs.
+#if !defined(ARDUINO)
+
 #include "synth_registry.h"
 #include <cstring>
 #include <algorithm>
@@ -158,3 +164,6 @@ const char* nodedef_suggest_param(const NodeDefDescriptor* def,
 }
 
 } // namespace sig
+
+
+#endif  // !defined(ARDUINO)