feat: add C API test infrastructure with foreign method binding support

Add a new test framework for exercising the Wren C embedding API directly from C code, including a Makefile target, test runner modifications, and the first API test case for boolean return values. The build system now compiles test sources from `test/api/` into a separate test executable, and the CLI's `createVM` and `runFile` functions accept an optional `WrenBindForeignMethodFn` callback to enable foreign method binding in tests. The test runner (`script/test.py`) is refactored to support both script and API test types, passing the test name instead of the full path for API tests. The initial `return_bool` test verifies that `wrenReturnBool` correctly returns `true` and `false` from foreign methods.

test/api/main.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "io.h"
+#include "vm.h"
+#include "wren.h"
+
+#include "return_bool/return_bool.h"
+
+// The name of the currently executing API test.
+const char* testName;
+
+static WrenForeignMethodFn bindForeign(
+    WrenVM* vm, const char* module, const char* className,
+    bool isStatic, const char* signature)
+{
+  if (strcmp(module, "main") != 0) return NULL;
+
+  // For convenience, concatenate all of the method qualifiers into a single
+  // signature string.
+  char fullName[256];
+  fullName[0] = '\0';
+  if (isStatic) strcat(fullName, "static ");
+  strcat(fullName, className);
+  strcat(fullName, ".");
+  strcat(fullName, signature);
+
+  if (strcmp(testName, "return_bool") == 0)
+  {
+    return returnBoolBindForeign(fullName);
+  }
+
+  fprintf(stderr,
+      "Unknown foreign method '%s' for test '%s'\n", fullName, testName);
+  return NULL;
+}
+
+int main(int argc, const char* argv[])
+{
+  if (argc != 2)
+  {
+    fprintf(stderr, "Usage: wren <test>\n");
+    return 64; // EX_USAGE.
+  }
+
+  testName = argv[1];
+
+  // The test script is at "test/api/<test>/<test>.wren".
+  char testPath[256];
+  strcpy(testPath, "test/api/");
+  strcat(testPath, testName);
+  strcat(testPath, "/");
+  strcat(testPath, testName);
+  strcat(testPath, ".wren");
+
+  runFile(bindForeign, testPath);
+  return 0;
+}

test/api/return_bool/return_bool.c

@@ -0,0 +1,21 @@
+#include <string.h>
+
+#include "wren.h"
+
+static void returnTrue(WrenVM* vm)
+{
+  wrenReturnBool(vm, true);
+}
+
+static void returnFalse(WrenVM* vm)
+{
+  wrenReturnBool(vm, false);
+}
+
+WrenForeignMethodFn returnBoolBindForeign(const char* signature)
+{
+  if (strcmp(signature, "static Api.returnTrue") == 0) return returnTrue;
+  if (strcmp(signature, "static Api.returnFalse") == 0) return returnFalse;
+
+  return NULL;
+}

test/api/return_bool/return_bool.h

@@ -0,0 +1,3 @@
+#include "wren.h"
+
+WrenForeignMethodFn returnBoolBindForeign(const char* signature);

test/api/return_bool/return_bool.wren

@@ -0,0 +1,7 @@
+class Api {
+  foreign static returnTrue
+  foreign static returnFalse
+}
+
+IO.print(Api.returnTrue)  // expect: true
+IO.print(Api.returnFalse) // expect: false