Add comprehensive integration tests that don't require Docker:
- test_xmlrpc_subprocess.py: Tests XmlRpcMiddleware against a real
subprocess-based XML-RPC server. Covers connection, variable
discovery, get/set operations, and flowgraph control (18 tests).
- test_mcp_runtime.py: Tests MCP runtime tools via FastMCP Client.
Verifies connect, disconnect, list_variables, get_variable,
set_variable, and flowgraph control work end-to-end (15 tests).
- test_fm_scanner.py: Tests signal probe functionality and FM scanner
parsing. Includes unit tests for helper functions and integration
tests for flowgraph construction with signal probe blocks (18 tests).
All 59 integration tests pass. These tests provide faster feedback
than Docker-based tests while still exercising real XML-RPC
communication and flowgraph construction.
