feat: implement complete descriptor collection system
feat: implement complete descriptor collection system
- Add comprehensive builder pattern (CollectDescriptorsOption) for configurable downloads
- Add atomic file operations using temporary files with rename for data integrity
- Implement file modification time comparison to skip unchanged files
- Add extraneous file cleanup with concurrent deletion using JoinSet
- Implement streaming downloads with size validation and progress tracking
- Add comprehensive error handling and structured logging throughout
- Support configurable concurrent download limits (default: 100)
- Add proper URL construction and validation for remote resources