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_coverage.py

@@ -1,8 +1,10 @@
-import pytest
 import asyncio
 import struct
-from openttd.protocol import OpenTTDProtocol, PacketGameType
+
+import pytest
 from openttd.client import OpenTTDClient
+from openttd.protocol import OpenTTDProtocol, PacketGameType
+
 
 class MockTransport:
     def __init__(self): self._closing = False
@@ -10,16 +12,19 @@ class MockTransport:
     def close(self): self._closing = True
     def write(self, data): return len(data)
 
+class FakeNetworkError(OSError):
+    """Stand-in for a socket-level failure, so it matches the client's narrowed handlers."""
+
 class MockProtocol:
     async def send_packet(self, data):
-        raise Exception("Send failed")
+        raise FakeNetworkError("Send failed")
 
 @pytest.mark.asyncio
 async def test_client_connect_exception(monkeypatch):
     # Coverage for client.py:51-53
     client = OpenTTDClient(host="127.0.0.1")
     async def mock_fail(*args, **kwargs):
-        raise Exception("Async Failure")
+        raise FakeNetworkError("Async Failure")
     monkeypatch.setattr(asyncio.get_running_loop(), "create_connection", mock_fail)
     with pytest.raises(Exception, match="Async Failure"):
         await client.connect()