Add configure_path() function that detects user's shell (zsh, bash, fish)
and automatically appends PATH configuration to the appropriate rc file.
Handles macOS vs Linux differences for bash (.bash_profile vs .bashrc).
Avoids duplicates by checking for existing klaas installer entries.

Add InputMode and InputConfig types to types.rs with support for
host-only, auto-lock, and free-for-all input modes. Add SessionConfig
to config.rs for loading input config from TOML. Update websocket.rs
to include InputConfigWire in session_attach messages. Add lock
message variants (LockAcquired, LockReleased, InputRejected) to
IncomingMessage for future guest mode support.