test: add comprehensive unit tests for mcp_integrated_planner_graph

- Add 50+ test cases covering helper functions, MCPIntentClassifier, and
  MCPPlannerGraph
- Test all helper functions: _extract_message_text, _detect_complex_query,
  _calculate_agent_timeout, etc.
- Test MCPIntentClassifier with all intent types (equipment, operations,
  safety, document, forecasting, general, ambiguous)
- Test MCPPlannerGraph initialization, routing, agent methods, and error
  handling
- Test edge cases: timeouts, empty messages, initialization failures,
  fallback responses
- Use proper mocking to avoid external dependencies
- Should significantly improve code coverage for mcp_integrated_planner_graph.py
  (currently 101 lines uncovered)

Author: T-DevH