feat(pdftract-64p5): implement classify CLI subcommand and --auto flag
- Implement pdftract classify command with JSON output
- Load built-in profiles + custom profiles from --profiles DIR
- Output format: {"document_type":"invoice","confidence":0.87,"reasons":[...],"runner_up":"receipt","runner_up_confidence":0.42}
- Support --top-k, --exit-on-unknown, --pretty flags
- Implement --auto flag for extract subcommand
- Add path traversal protection for profiles directory
- Add load_profiles_from_file() and load_profiles_from_dir() to profiles/loader
Closes: pdftract-64p5
adaf27be85