feat: adding arm packaging and runtime support (ubuntu 24.04)

[ursuciprian]

• add ARM64/aarch64 packaging support for .deb, tarball, AppImage naming, and Arch PKGBUILD
• fix libghostty GLAD static linking so ARM release builds resolve Ghostty GL loader symbols
• add WebKitGTK runtime fallbacks for restricted DRM/GBM and sandbox issues on ARM/NVIDIA systems
• document Ubuntu ARM64 install/package artifact names

Ubuntu 24.04 ships blueprint-compiler 0.12.0, but Ghostty packaging requires >= 0.16.0. For local ARM packaging validation, I used a local venv with blueprint-compiler==0.20.4 ahead of /usr/bin on PATH.

[bvolpato]

PR currently conflicts with main and needs rebase before review can converge.

Blocking packaging issues:

• ARM artifacts referenced by README.md and PKGBUILD.template are never produced. release-linux.yml still runs one x86_64 job and uses x86_64 appimagetool, so ARM deb/tarball/AppImage URLs will not exist.
• PKGBUILD.template renamed checksum tokens, but aur-publish.yml still replaces only @@sha256@@. Generated PKGBUILD retains both new placeholders and breaks existing x86_64 AUR publishing.
• LIMUX_ARCH changes labels and package metadata without changing Zig/Cargo targets or target output paths. It can package native x86_64 binaries as arm64 artifacts.

nonblocking: WEBKIT_DISABLE_DMABUF_RENDERER and WEBKIT_WEBGL_DISABLE_GBM now default on for every GPU and architecture. Scope fallback to affected systems or avoid making degraded rendering universal.

Architecture mapping, unsupported-architecture rejection, GLAD whole-archive linking, and icon lookup changes otherwise look reasonable.

Recommendation: rebase onto current main, add real ARM release production and checksum wiring, and make architecture override build selected target or remove it.

(Review assisted by gpt-5.6-sol)