Implements the ahfail-display binary crate: GTK popup window that spawns
the Nedry sprite and plays the audio clip, with SIGTERM handling, 15-minute
failsafe, deadzone CLI parsing, volume save/restore, and update check.
Adds a build.rs that compiles GResources via glib-compile-resources so the
binary can be built with plain `cargo build` outside of Meson.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
