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]>

main_admin.py

@@ -1,13 +1,13 @@
 import asyncio
 import logging
-import sys
 import os
+import sys
 
 # Add the lib directory to sys.path so we can import the openttd package
 sys.path.append(os.path.join(os.path.dirname(__file__), 'lib'))
 
 from openttd import OpenTTDAdminClient
-from openttd.protocol import AdminUpdateType, AdminUpdateFrequency
+from openttd.protocol import AdminUpdateFrequency, AdminUpdateType
 
 # Configuration
 SERVER_HOST = "127.0.0.1"
@@ -82,14 +82,14 @@ async def run_admin():
                     print(f"    waiting by next hop: {flow['waiting_by_via']}")
                     print(f"    planned by source: {flow['planned_by_from']}")
                     print(f"    planned by next hop: {flow['planned_by_via']}")
-            except Exception as e:
+            except Exception as e:  # noqa: BLE001 - demo script: one failed station query should not abort the walk
                 print(f"!!! station query failed: {e}")
 
         await asyncio.sleep(5)
         print("--- Quitting ---")
         await admin.quit()
 
-    except Exception as e:
+    except Exception as e:  # noqa: BLE001 - top-level demo handler: report any failure instead of dumping a traceback
         print(f"!!! Error: {e}")
 
 if __name__ == "__main__":