[QA] Strengthen CommunicationManager tests with real protobuf contracts

[mayaparov]

Summary

Strengthen CommunicationManager unit tests by validating real protobuf contracts (serialized bytes → proto_capi.Message parsing, oneof arm selection, order handling) while keeping ZeroMQ fully mocked (no network I/O).

The test suite also auto-prepares protobuf Python modules when missing/stale via the existing toolchain, and cleans up any newly generated artifacts to avoid polluting the working tree.

Motivation

CommunicationManager is an infrastructure component where regressions are easy to introduce and hard to detect (socket identity/timeouts, reply validation, message ordering). Earlier tests were not sufficiently tied to the real protobuf schema, so certain proto changes (field removal/oneof reshaping) could slip through unnoticed.

This PR makes the tests schema-sensitive by parsing and asserting against real generated protobuf message classes, while preserving deterministic and CI-friendly execution in minimal environments.

Changes

• Updated tests in opencda/core/common/communication/test/test_communication_manager.py to:
  • mock zmq via sys.modules (no real sockets / no network);
  • use real protobuf modules and parse sent/received bytes into proto_capi.Message;
  • assert oneof arm selection (opencda / artery), order, and message_order invariants;
  • cover negative cases (send timeout, receive timeout, unexpected message content, wrong order).
• Added a session-scoped protobuf readiness fixture that:
  • validates the minimal expected schema for proto_capi.Message;
  • generates missing/stale pb2 modules using CommunicationToolchain (only when required);
  • temporarily adjusts sys.path to support top-level imports inside generated code;
  • cleans up only newly created generated artifacts after the session.

How to run

uv run pytest -q opencda/core/common/communication/test/test_communication_manager.py
uv run pytest -q