Support multiple agent CLI tools (Gemini CLI, Codex CLI, etc.)

[jsleemaster]

Summary

Support agent CLI tools beyond Claude Code, such as Gemini CLI, Codex CLI, and others.

Details

Currently cltree only supports Claude Code. This issue tracks the work to make cltree a universal companion for various agent CLI tools.

Key Tasks

• Extract PTY execution command into a config file (~/.config/cltree/config.toml)
• Implement config file system (TOML parsing, defaults, validation)
• Add CWD detection logic for each CLI tool
• Support CLI presets (claude, gemini, codex, etc.)

Related Files

• src/terminal.rs - PTY creation and process execution
• src/vterm.rs - CWD detection logic
• src/app.rs - App configuration management