feat(test): add comprehensive test infrastructure

- Add test target to both bmake.mk and gmake.mk Makefiles
- Add test-related artifacts to .gitignore (excluding DLLs/shared libs)
- Create test directory with cross-platform Makefiles (bmake.mk, gmake.mk)
- Implement cross-platform test program with signal handling (test.c)
- Add test module source for compilation (test_mod.c)
- Set up automated test environment with mods/ directory
- Support both POSIX and Windows platforms

The test infrastructure allows running integration tests via 'make test'
and demonstrates stk library functionality with dynamic module loading.
Generated DLLs/shared libraries are excluded from version control.

test/test.c

@@ -0,0 +1,76 @@
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stk.h>
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <unistd.h>
+#endif
+
+volatile sig_atomic_t stop;
+
+#ifdef _WIN32
+BOOL WINAPI console_handler(DWORD signal)
+{
+	if (signal == CTRL_C_EVENT) {
+		stop = 1;
+		printf("\nCaught Ctrl+C, shutting down...\n");
+		return TRUE;
+	}
+	return FALSE;
+}
+#else
+void inthand(int signum)
+{
+	stop = 1;
+	printf("\nCaught SIGINT, shutting down...\n");
+}
+#endif
+
+int main(int argc, char **argv)
+{
+	uint8_t init_result;
+	uint64_t iterations = 0;
+
+	printf("stk test - CTRL+C to exit\n");
+
+#ifdef _WIN32
+	if (!SetConsoleCtrlHandler(console_handler, TRUE)) {
+		fprintf(stderr,
+			"ERROR: Could not set console control handler\n");
+		return EXIT_FAILURE;
+	}
+#else
+	signal(SIGINT, inthand);
+#endif
+
+	init_result = stk_init();
+	if (init_result != STK_INIT_SUCCESS) {
+		fprintf(stderr, "FAIL: stk_init() returned %d\n", init_result);
+		return EXIT_FAILURE;
+	}
+
+	while (!stop) {
+		size_t events = stk_poll();
+		if (events > 0)
+			printf("Poll: %lu module event(s) detected\n", events);
+
+		iterations++;
+		if (iterations % 5 == 0) {
+			printf("Still running... (iteration %lu)\n",
+			       iterations);
+		}
+#ifdef _WIN32
+		Sleep(1000);
+#else
+		sleep(1);
+#endif
+	}
+
+	printf("Shutting down stk...\n");
+	stk_shutdown();
+
+	return EXIT_SUCCESS;
+}