Close TCP connection after synthesis so HA receives FIN and unblocks

disconnect() was a no-op in the base class; writer.close() was never
called, leaving HA waiting for a TCP FIN that never arrived.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server.py

@@ -83,6 +83,13 @@ class KokoroEventHandler(AsyncEventHandler):
         self.config = config
         self.executor = executor
 
+    async def disconnect(self) -> None:
+        self.writer.close()
+        try:
+            await self.writer.wait_closed()
+        except Exception:
+            pass
+
     async def handle_event(self, event: Event) -> bool:
         if Describe.is_type(event.type):
             await self.write_event(self.wyoming_info.event())