Rust port of GNU nano 9.0.0. Highlights:
- Fix sluggish typing/backspace (input no longer lags during fast typing or held keys)
- Resolve the home directory on Windows
- Buffer terminal output through a single writer
- Cross-platform self-updater: --install / --update / --force, plus a background
  update check (Windows on by default; Linux opt-in via NANO_UPDATE_CHECK)
- `nano --version` reports both the upstream GNU nano version and the nano-rs version

Assets:
- nano-amd64.exe, nano-arm64.exe — Windows (static CRT, no VC++ redist needed)
- nano-linux-amd64, nano-linux-arm64 — Linux (musl, fully static)