fix: GFK client Windows compatibility - replace pkill with taskkill

- Replace Linux-only 'pkill' command with cross-platform solution
- Use 'wmic' and 'taskkill' on Windows to kill existing Python processes
- Add CREATE_NEW_PROCESS_GROUP for proper signal handling on Windows
- Improve shutdown handling for both platforms

Fixes FileNotFoundError: [WinError 2] when starting GFK on Windows.

gfk/client/mainclient.py

@@ -3,36 +3,82 @@ import os
 import time
 import sys
 import signal
+import platform
 
+IS_WINDOWS = platform.system() == 'Windows'
 
 scripts = ['quic_client.py', 'vio_client.py']
 
 
+def kill_existing_script(script_name):
+    """Kill any existing instance of the script (cross-platform)"""
+    if IS_WINDOWS:
+        # On Windows, use taskkill to find and kill python processes
+        try:
+            result = subprocess.run(
+                ['wmic', 'process', 'where',
+                 f"commandline like '%{script_name}%' and name like '%python%'",
+                 'get', 'processid'],
+                capture_output=True, text=True, stderr=subprocess.DEVNULL
+            )
+            for line in result.stdout.split('\n'):
+                line = line.strip()
+                if line.isdigit():
+                    subprocess.run(['taskkill', '/F', '/PID', line],
+                                 stderr=subprocess.DEVNULL, stdout=subprocess.DEVNULL)
+        except Exception:
+            pass
+    else:
+        subprocess.run(['pkill', '-f', script_name], stderr=subprocess.DEVNULL)
+
+
 def run_script(script_name):
-    # Use sys.executable to run with the same Python interpreter (venv)
-    subprocess.run(['pkill', '-f', script_name], stderr=subprocess.DEVNULL)
+    """Start a script, killing any existing instance first"""
+    kill_existing_script(script_name)
     time.sleep(0.5)
-    p = subprocess.Popen([sys.executable, script_name])
+
+    if IS_WINDOWS:
+        p = subprocess.Popen([sys.executable, script_name],
+                           creationflags=subprocess.CREATE_NEW_PROCESS_GROUP)
+    else:
+        p = subprocess.Popen([sys.executable, script_name])
     return p
 
 
 processes = []
-def signal_handler(sig, frame):
-    print('You pressed Ctrl+C!')
-    for p in processes:
-        print("terminated:",p)
-        p.terminate()
 
+
+def signal_handler(sig, frame):
+    print('\nShutting down GFK client...')
+    for p in processes:
+        try:
+            p.terminate()
+            p.wait(timeout=3)
+        except Exception:
+            try:
+                p.kill()
+            except Exception:
+                pass
     sys.exit(0)
 
 
 if __name__ == "__main__":
+    signal.signal(signal.SIGINT, signal_handler)
+    if not IS_WINDOWS:
+        signal.signal(signal.SIGTERM, signal_handler)
+
+    print("Starting GFK client...")
     p1 = run_script(scripts[0])
     time.sleep(1)
     p2 = run_script(scripts[1])
-    processes.extend([p1, p2])  # Modify global list, don't shadow it
-    signal.signal(signal.SIGINT, signal_handler)
-    p1.wait()
-    p2.wait()
-    print("All subprocesses have completed.")
+    processes.extend([p1, p2])
+
+    print("GFK running. Press Ctrl+C to stop.\n")
+
+    try:
+        p1.wait()
+        p2.wait()
+        print("All subprocesses have completed.")
+    except KeyboardInterrupt:
+        signal_handler(None, None)