Reset Python interpreter if already initialized

Instead of skipping initialization when the Python interpreter is already running, finalize the existing interpreter and reinitialize it. This ensures a fresh interpreter state and avoids issues with a potentially wedged event loop from previous sessions.

Author: FeodorFitsner

src/serious_python_android/lib/src/cpython.dart

@@ -122,12 +122,14 @@ Future<String> runPythonProgramInIsolate(List<Object> arguments) async {
     cpython.Py_Initialize();
     _pyLog("after Py_Initialize()");
   } else {
-    // Interpreter is already running; skip launching another run and let the
-    // previously started script continue. Return a message for the caller.
-    _pyLog("Python already initialized; skipping new run");
-    final msg = "Python already initialized; skipped starting a new run.";
-    sendPort.send(msg);
-    return msg;
+    // Interpreter was left running (likely from a previous app session). Tear
+    // it down and start fresh to avoid reusing a wedged event loop.
+    _pyLog("Python already initialized; finalizing stale interpreter");
+    cpython.PyGILState_Ensure(); // ensure we own the GIL before finalizing
+    cpython.Py_FinalizeEx();
+    _pyLog("after Py_FinalizeEx(), reinitializing");
+    cpython.Py_Initialize();
+    _pyLog("after Py_Initialize() (fresh)");
   }
 
   var result = "";