Pixel VR Player v1.3.0 - one-command install with automatic Steam library entry

Installing no longer needs manual extraction or fiddling with Steam's Non-Steam Games dialog.

One command

From a terminal on the headset (Desktop Mode or over SSH):

curl -fsSL https://raw.githubusercontent.com/Pixelplanet/Pixel-VR-Player/main/tools/install.sh | sh

The installer:

• downloads the latest ARM64 release and verifies its SHA-256 checksum;
• installs the binary, launcher and shaders to ~/PixelVRPlayer;
• adds "Pixel VR Player" to your Steam library as a Non-Steam Game, so it is
  launchable from Game Mode without any manual setup (VR flag set, so Steam
  starts SteamVR for you);
• backs up shortcuts.vdf before touching it and preserves every existing
  Non-Steam shortcut;
• checks the binary's shared libraries and warns if anything is missing.

Restart Steam afterwards if it was already running, or pass --restart-steam to
have the installer close and reopen it automatically.

Option	Effect
--dir DIR	install somewhere other than ~/PixelVRPlayer
--version vX.Y.Z	install a specific release instead of the latest
--no-steam	skip the Steam library entry
--restart-steam	close Steam first, then reopen it
--uninstall	remove the app and its Steam shortcut
--force	install on a non-aarch64 machine

Upgrading is the same command again. Settings (~/.config/pixelvr) and cached
thumbnails (~/.cache/pixelvr) live outside the install directory and are never
touched.

Offline install

Download pixelvr-linux-arm64.tar.gz, copy it to the headset, extract it and run
./install.sh — the tarball now ships the installer and a VERSION file. Or run
./run.sh directly if you prefer to keep things portable.

Also in this release

• Every release now publishes pixelvr-linux-arm64.tar.gz.sha256, and the
  workflow syntax-checks the installer scripts before building.

Full changelog: v1.2.0...v1.3.0