feat: implement environment details caching to reduce duplicate processing

- Add EnvironmentDetailsCache class with section-based hashing
- Implement change detection for VSCode files, tabs, terminals, cost, mode
- Add configurable TTL for different section types
- Modify getEnvironmentDetails to use caching for performance optimization
- Add comprehensive test suite for caching mechanism
- Maintain backward compatibility with existing API

Fixes #5844

Author: roomote