Replace Vec<u8> with memmap2::Mmap for file content. Build line index via BufReader streaming (from_reader) instead of scanning mmap'd data, keeping RSS at ~3MB for 5GB files instead of ~5GB.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Rewrite LineIndex to use sparse sampling (every 256 lines) instead of per-line offsets. Add from_reader() for low-RSS streaming index construction via BufReader fill_buf()/consume(), reducing 5GB file RSS from 5122MB to 3.4MB.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Add level detection that tries JSON parsing first (trusts level field), then falls back to keyword scanning with word-boundary checks. Supports SEVERE, FATAL, ERROR, WARN, INFO, DEBUG, TRACE and their abbreviations.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
Replace empty AppConfig stub with ColorConfig struct that stores level-to-color mappings as strings. Supports loading/saving from XDG config directory via TOML, with graceful degradation on missing/invalid files.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
