issue 190: Add Windows signal handling support

Add platform-specific signal handling to enable Ctrl+C cancellation on Windows.
- Windows uses SetConsoleCtrlHandler with CTRL_C_EVENT
- Unix continues to use signal() with SIGINT
- Unified setup_signal_handler() function for both platforms

src/main.cpp

@@ -29,16 +29,38 @@
 #include <filesystem>
 #include <random>
 #include <iomanip>
+#ifndef _WIN32
 #include <signal.h>
+#else
+#include <windows.h>
+#endif
 
 std::atomic<bool> ctrlc_request;
 
+#if defined(_WIN32)
+BOOL WINAPI console_handler(DWORD ctrl_type) {
+    if (ctrl_type == CTRL_C_EVENT) {
+        ctrlc_request = true;
+        return TRUE;
+    }
+    return FALSE;
+}
+
+void setup_signal_handler() {
+    SetConsoleCtrlHandler(console_handler, TRUE);
+}
+#else
 void signalHandler(int signal) {
     if (signal == SIGINT) {
         ctrlc_request = true;
     }
 }
 
+void setup_signal_handler() {
+    signal(SIGINT, signalHandler);
+}
+#endif
+
 static const std::vector<AgentProfile> profiles = {
 #if !defined(_WIN32)
     {
@@ -106,7 +128,7 @@ static HarnessState read_harness_state_or_exit(const char* file_path) {
 }
 
 int main(int argc, char** argv) {
-    signal(SIGINT, signalHandler);
+    setup_signal_handler();
 
     OllamaConfig cfg;
     if (const char* m = std::getenv("OLLAMA_MODEL")) cfg.model    = m;