Complete Phase 1: Build KiCad with optional dependencies disabled

Add CMake override modules, stub implementations, and patches to build
KiCad without CURL, libgit2, OpenCASCADE, and ngspice dependencies.

- cmake/: Find modules that provide stub targets when deps disabled
- stubs/include/: Header stubs for curl, git2, ngspice, OCC
- stubs/src/: Implementation stubs for disabled features
- patches/: Consolidated patch for KiCad source modifications
- scripts/: Build helper scripts

Verified full native build on macOS with all optional deps disabled.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

stubs/include/ngspice/sharedspice.h

@@ -0,0 +1,90 @@
+/*
+ * KiCad Wasm Port - ngspice sharedspice.h stub
+ *
+ * Provides stub declarations when ngspice is disabled.
+ */
+
+#ifndef NGSPICE_SHAREDSPICE_H
+#define NGSPICE_SHAREDSPICE_H
+
+// Version information (stub)
+#define NGSPICE_PACKAGE_VERSION "disabled"
+
+// ngspice types
+typedef int NG_BOOL;
+
+// Callback function types (as used by ngspice)
+// These are function types, not function pointer types.
+// So SendChar* is a function pointer type.
+typedef int SendChar(char*, int, void*);
+typedef int SendStat(char*, int, void*);
+typedef int ControlledExit(int, NG_BOOL, NG_BOOL, int, void*);
+typedef int SendData(void*, int, int, void*);
+typedef int SendInitData(void*, int, void*);
+typedef int BGThreadRunning(NG_BOOL, int, void*);
+typedef int GetVSRCData(double*, double, char*, int, void*);
+typedef int GetISRCData(double*, double, char*, int, void*);
+typedef int GetSyncData(double, double*, double, int, int, int, void*);
+
+// ngspice is loaded dynamically via dlopen/GetSymbol, so we don't need to
+// provide stub implementations for the functions. KiCad will get nullptr
+// from GetSymbol when ngspice is not available, and handle it appropriately.
+
+// However, we do need to provide the vector_info struct since it's used
+// when processing data from ngspice.
+struct vector_info;
+typedef struct vector_info* pvector_info;
+
+// Basic type definitions that might be used
+typedef struct {
+    char* name;
+    char* type;
+    void* data;
+} vecvalues;
+
+typedef struct {
+    char* name;
+    int veccount;
+    vecvalues* vecarray;
+} vecvaluesall;
+
+typedef struct {
+    char* name;
+    char* type;
+    int length;
+} vecinfo;
+
+typedef struct {
+    char* name;
+    char* title;
+    char* date;
+    char* type;
+    int veccount;
+    vecinfo** vecs;
+} vecinfosall;
+
+typedef struct {
+    double progress;
+    double value;
+} plotmsg;
+
+// ngcomplex_t is a complex number with cx_real and cx_imag
+typedef struct ngcomplex {
+    double cx_real;
+    double cx_imag;
+} ngcomplex_t;
+
+// vector_info struct - matches the real ngspice definition
+// Note: pvector_info is forward-declared above as struct vector_info*
+struct vector_info {
+    char* v_name;       // name of the vector
+    int v_type;         // type of vector
+    short v_flags;      // various flags
+    double* v_realdata; // real data (if real vector)
+    ngcomplex_t* v_compdata; // complex data (if complex vector)
+    int v_length;       // length of the vector
+    int v_numdims;      // number of dimensions (1 for scalar/vector)
+    int v_dims[8];      // dimension sizes
+};
+
+#endif // NGSPICE_SHAREDSPICE_H