Fix #10 + #11: transport hardening + controller resource leaks

#10 transport (obdcore/transport.py):
- TcpTransport.read raises IOError on a real socket error or peer-close instead
  of swallowing it as a timeout, so a dead WiFi link surfaces (via the #8 poll
  handler) as 'connection lost' rather than a frozen dashboard.
- TcpTransport.reset_input_buffer drains at most 64 chunks — never spins forever.
- BleTransport closes the client + stops the event-loop thread on connect
  timeout (no leak), caps the notification buffer at 64 KiB, and close() is
  robust when only partially initialised.

#11 controller (gui/controller.py, obdcore/store.py):
- connect() closes the transport and nulls the link if init()/connect() raises,
  so a failed/retried connect doesn't orphan sockets/threads.
- stop_record() unhooks store.recorder BEFORE closing it, and CsvRecorder now
  has a 'closed' guard so a poll-thread write racing close() is a no-op instead
  of an I/O-on-closed-file crash.

Closes #10
Closes #11

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016yT89n4zR4qbrySoSiEyZs

obdcore/store.py

@@ -128,13 +128,19 @@ class CsvRecorder:
         self._f = open(path, "w")
         self._f.write("t,key,value\n")
         self._lock = threading.Lock()
+        self._closed = False
 
     def write(self, key, t, v):
         with self._lock:
+            if self._closed:                  # a poll-thread write racing close() is a no-op
+                return
             self._f.write(f"{t:.3f},{key},{'' if v is None else v}\n")
 
     def close(self):
         with self._lock:
+            if self._closed:
+                return
+            self._closed = True
             self._f.close()