Fixes a bug where the root decision was recorded as 'strategy_choice' instead of
the correct 'prompt_definition' type during the Strategize phase. The decision tree
now correctly records the plan's prompt/description as the root decision, ensuring
proper decision tree structure and downstream decision evaluation.
Changes:
- Modified start_strategize() to record prompt_definition as the root decision
- Updated decision question to 'What is the plan prompt?'
- Set chosen_option to plan.description with fallback to action_name or plan_id
- Added test scenario to verify root decision type is prompt_definition
Closes#9061
HAL9000