Fix ruff lint findings across client, protocol, and tests

Resolve 51 findings from the I/RUF/BLE/TRY002/S110/PLR0402 rule set:

- Sort imports and __all__ (I001, RUF022, PLR0402). The sys.path.insert
  calls in check_public_calls.py and tests/test_e2e.py still precede the
  openttd imports that depend on them.
- Replace unused unpacked values with _ (RUF059) and annotate the two
  timetable lookup tables as ClassVar (RUF012).
- Narrow the best-effort excepts in OpenTTDClient.quit and
  OpenTTDAdminClient.quit to (OSError, SocketClosed) and log at debug
  rather than swallowing silently (BLE001, S110). The test doubles now
  raise an OSError subclass so they still exercise that branch.
- Narrow the gamescript JSON fallback to json.JSONDecodeError. The broad
  catch in receive_packet keeps a noqa: it guards untrusted wire data and
  must degrade to a no-op packet instead of killing the connection.
- Use contextlib.suppress instead of try/except/pass in tests.

ruff check . is clean, 102 tests pass, coverage stays at 100%.

Co-Authored-By: Claude <[email protected]>

tests/test_admin.py

@@ -1,10 +1,15 @@
-import pytest
 import asyncio
 import json
 import os
+
 import monocypher
+import pytest
 from openttd import OpenTTDAdminClient
-from openttd.protocol import PacketAdminType, AdminUpdateType, AdminUpdateFrequency
+from openttd.protocol import AdminUpdateFrequency, AdminUpdateType, PacketAdminType
+
+
+class FakeNetworkError(OSError):
+    """Stand-in for a socket-level failure, so it matches the client's narrowed handlers."""
 
 def decode_gamescript_payload(packet):
     """Decode the JSON payload of an AdminGamescript packet (2-byte length + 1-byte type + string)."""
@@ -84,7 +89,7 @@ async def test_admin_client_connect_and_actions(monkeypatch):
 
     # 3. Connect Exception
     async def mock_fail(*args, **kwargs):
-        raise Exception("Connection Failed")
+        raise FakeNetworkError("Connection Failed")
     monkeypatch.setattr(asyncio.get_running_loop(), "create_connection", mock_fail)
     with pytest.raises(Exception, match="Connection Failed"):
         await client.connect()
@@ -196,7 +201,7 @@ async def test_admin_client_connect_and_actions(monkeypatch):
     # 8. Quit Exception
     class BadProtocol:
         async def send_packet(self, data):
-            raise Exception("Fail")
+            raise FakeNetworkError("Fail")
     client._transport = MockTransport()
     client._protocol = BadProtocol()
     await client.quit()