Add unit tests for LSS master (coverage 42% → 93%)

[bizfsc]

Summary

Add 28 unit tests for canopen/lss.py to improve test coverage from 42% to 93%.

Tests Added

• Switch state commands: global configuration/waiting mode, selective with match/no-match
• Node ID configuration: set node ID, error response handling
• Bit timing configuration: set bit timing, activate with delay
• Store configuration: success and error responses
• LSS address inquiry: vendor ID, product code, revision number, serial number
• Timeout handling: verify LssError raised on missing responses
• Fast scan: full protocol flow with binary search
• Obsolete aliases: send_switch_state_global backward compat
• LssError: exception instantiation and inheritance

Approach

Uses unittest.mock.MagicMock to mock the network layer. A helper method injects CAN responses during send_message() calls to simulate real LSS slave behavior, including only responding to commands that expect a reply per the protocol.

Coverage

canopen/lss.py    42% → 93%
Overall           77% → 80%