Feature idea: RAII guard for raw mode #45

A RawModeGuard type that calls enable_raw_mode() in its constructor and disable_raw_mode() in its destructor would make terminal-state restoration automatic and exception-safe, instead of relying on every call site remembering to clean up manually (see the sample-app terminal-leak bug in this repo).

Suggested branch: feat/raw-mode-guard
Suggested PR title: feat(config): add RAII guard for raw mode