Add E2E integration tests for MQTT bridge, CLI, and device profiler

[groupsky]

Summary

The E2E testing infrastructure is now in place (PR #236), but the actual integration tests for the following components are not yet implemented:

Test Scenarios to Implement

1. MQTT Bridge Tests

• Single device: Bridge publishes data to MQTT topics
• Multiple devices: Correct polling and topic separation
• Bus contention: No mutex issues with concurrent device access
• Error handling: Device disconnection and reconnection
• Data accuracy: Published values match emulator configuration

2. CLI Tests

• ya-modbus read: Reads correct values from emulated devices
• ya-modbus write: Updates registers successfully
• ya-modbus list-devices: Shows available drivers
• Error handling: Invalid commands, connection failures
• Help text: Displays correctly

3. Device Profiler Tests

• Device discovery: Finds devices on serial port
• Slave ID detection: Identifies correct slave IDs
• Baud rate detection: Detects communication parameters
• Device type identification: Matches known driver patterns

Infrastructure Ready

The test infrastructure from PR #236 provides:

• ✅ Virtual serial ports (socat)
• ✅ Emulator with RTU transport
• ✅ MQTT broker (Docker Compose)
• ✅ BATS test framework
• ✅ Helper functions and setup scripts
• ✅ CI/CD workflow

Related

Part of the E2E testing roadmap. Infrastructure completed in PR #236.

[groupsky]

✅ VERIFIED FIXED: Comprehensive E2E tests implemented for all three components:

• MQTT Bridge: 03-mqtt-bridge.bats (8 tests) covering single/multi-device, disconnection, reconnection, data accuracy
• CLI: 04-cli.bats (51 tests) covering read, write, list-devices, error handling, help text
• Device Profiler: Integrated in 04-cli.bats (23 discover tests) covering discovery, filters, output formats
  Total: 82 comprehensive E2E tests.