Adds a bell-leak-check-gnome NixOS test (nix/tests.nix) that launches
Ghostty under GNOME on Wayland, rings 100 bells in the window, and fails
if the GUI process thread count grows per-bell — the end-to-end
signature of the GStreamer pipeline leak fixed in this branch. Verified
locally: growth of ~1 thread over 100 bells, vs ~+400 pre-fix.
Replaces the earlier Xvfb shell script + workflow job: per review, X11
support in GNOME is going away, and this belongs as a Nix check
alongside the other *-gnome tests rather than a standalone script.
The VM has no GPU, so it renders via llvmpipe; the test gives the guest
enough cores/RAM for software GL and tolerates the +new-window D-Bus
activation exceeding its client-side timeout (the window still comes up)
by waiting for the window rather than hard-failing on the call.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
As of NixOS/nixpkgs#473413[1], `zig.hook` no longer supports
`zig_default_flags`, and now they can and must be provided in
`zigBuildFlags` instead.
Updating also requires removing gnome-xorg since it has been removed
from nixpkgs.
[1] https://github.com/NixOS/nixpkgs/pull/473413
