Config class writes YAML (config.yaml), but xiaoyuzhou.py, cli.py, and
transcribe.sh were hardcoded to read config.json (JSON format). Users who
configured groq-key via 'agent-reach configure' would not have their key
detected because the wrong file was being read.
Fixes#128 (related to config loading)
Co-authored-by: Panniantong <panniantong@users.noreply.github.com>