docs(api): add comprehensive Godoc comments for all interfaces
- Add detailed Godoc for Loader, Capture, Parser, Engine interfaces
- Add detailed Godoc for Writer, UnixSocketWriter, MultiWriter, Builder
- Add detailed Godoc for Logger interface
- Enhance NewLogRecord documentation with pointer/omitempty behavior
- Enhance DefaultConfig documentation with default values
Implements code_style.comments.rules.godoc_exported from architecture.yml
Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>