- Added automatic context promotion feature that switches to larger-context models when approaching context limits.
- Added 'contextPromotion.enabled' setting to control automatic model promotion with default value of enabled.
- Added 'contextPromotion.thresholdPercent' setting to configure context usage threshold for triggering promotion with default value of 90%.
- Implemented context promotion logic in AgentSession that monitors token usage and automatically switches models when threshold is exceeded.
- Added provider session cleanup during model switches to properly handle session state transitions.
- Added comprehensive test coverage for context promotion functionality including threshold-based promotion and non-promotion scenarios.