feat(packaging): add Arch Linux packages

[Jsewill]

Add Arch Linux x86_64 packages to the existing build and release workflow. pnpm package:arch builds the current checkout with makepkg, packages the wallet and its built-in apps, and produces a pacman package alongside the other Tauri bundles. The launcher includes the documented NVIDIA explicit-sync workaround, and the packaging guide covers building, installing, and updating the package.

Native Wayland can place Logout and other bottom controls below the visible window because Tauri's resize event includes the GTK title bar. Size the main webview from GTK's content allocation only when GTK reports an active Wayland backend. X11 and XWayland keep Tauri's existing resize behavior, including when WAYLAND_DISPLAY is also set. The Arch package release is incremented to 4.

Validation on Arch Linux with Rust 1.98.1:

• pnpm exec tauri build --no-bundle -- --frozen (including frontend and built-in apps).
• cargo clippy -p sage-tauri --all-features --all-targets --frozen and cargo fmt --all -- --check.
• node --test scripts/package-arch.test.mjs, launcher/PKGBUILD syntax checks, and formatting of the updated guide.
• Native executable checks on Hyprland at 1150×1000 and 1280×900 using the real navigation components with mock wallet data in isolated profiles. Logout remains visible on Wayland. With GDK_BACKEND=x11 and WAYLAND_DISPLAY still set, viewport and Logout bounds match the unpatched binary.

Implementation assisted by Astra.

[Jsewill]

In addition to the arch packaging, I had Astra add a workaround for Tao's inner window sizing discrepancy under Wayland. Tao reports dimensions that include window decorations, and Tauri uses those dimensions for sage's main webview. Ideally this gets fixed upstream, but this should help in the meantime.