feat: GitHub builds the app; run it with curl

steamify-app.tar.gz (ui/, steamify.sh, lib/, icon) and its launcher
steamify-app.sh in every release: it installs to ~/.local/share/steamify/app,
installs PySide6 if needed, adds a launcher entry and starts the app.
STEAMIFY_BRANCH=<branch> runs a branch before it's released.

ui/steamify-app.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+# Steamify CachyOS - get and start the app (v2), for `curl | bash`:
+#   curl -fsSL https://github.com/theupriser/steamify-cachyos/releases/latest/download/steamify-app.sh | bash
+# Downloads the newest release's app package (steamify-app.tar.gz: the app,
+# steamify.sh and lib/) to ~/.local/share/steamify/app, installs PySide6 if
+# it's missing, adds a launcher entry, and starts the app.
+# STEAMIFY_BRANCH=<branch> takes that branch's source instead of a release
+# (for testing before a release).
+set -euo pipefail
+
+REPO="theupriser/steamify-cachyos"
+DEST="${XDG_DATA_HOME:-$HOME/.local/share}/steamify/app"
+APPS="${XDG_DATA_HOME:-$HOME/.local/share}/applications"
+
+say() { printf '\033[36m[INFO]\033[0m %s\n' "$*"; }
+die() { printf '\033[31m[ERROR] %s\033[0m\n' "$*" >&2; exit 1; }
+
+[[ $EUID -ne 0 ]] || die "Run this as your normal user, not as root."
+command -v pacman >/dev/null || die "This is for CachyOS/Arch (no pacman found)."
+
+tmp="$(mktemp -d)"; trap 'rm -rf "$tmp"' EXIT
+if [[ -n "${STEAMIFY_BRANCH:-}" ]]; then
+    say "Downloading Steamify from the $STEAMIFY_BRANCH branch..."
+    curl -fsSL "https://github.com/$REPO/archive/refs/heads/$STEAMIFY_BRANCH.tar.gz" -o "$tmp/src.tar.gz" ||
+        die "Couldn't download the $STEAMIFY_BRANCH branch."
+    mkdir "$tmp/app"
+    tar -xzf "$tmp/src.tar.gz" -C "$tmp/app" --strip-components=1
+else
+    say "Downloading the newest Steamify app..."
+    curl -fsSL "https://github.com/$REPO/releases/latest/download/steamify-app.tar.gz" -o "$tmp/app.tar.gz" ||
+        die "Couldn't download the app (is there a release with steamify-app.tar.gz yet?)."
+    mkdir "$tmp/app"
+    tar -xzf "$tmp/app.tar.gz" -C "$tmp/app"
+fi
+[[ -x "$tmp/app/ui/steamify-ui" && -f "$tmp/app/steamify.sh" ]] || die "The download doesn't contain the app."
+
+mkdir -p "$(dirname "$DEST")"
+rm -rf "$DEST.new"; mv "$tmp/app" "$DEST.new"
+rm -rf "$DEST"; mv "$DEST.new" "$DEST"
+say "Installed to $DEST ($(grep -m1 -oP '^VERSION=\K.*' "$DEST/steamify.sh"))."
+
+if ! python3 -c 'import PySide6.QtQml' 2>/dev/null; then
+    say "The app needs PySide6 (Qt for Python); installing it..."
+    # Piped in via curl, stdin isn't the terminal: sudo asks on it anyway.
+    sudo pacman -S --needed --noconfirm pyside6 </dev/tty || die "Installing pyside6 failed."
+fi
+
+# Launcher entry (its id also names the app to the desktop portal).
+mkdir -p "$APPS"
+cat > "$APPS/steamify-ui.desktop" << EOF
+[Desktop Entry]
+Type=Application
+Name=Steamify CachyOS
+Comment=Turn this PC into a SteamOS-style console
+Exec=$DEST/ui/steamify-ui
+Icon=$DEST/assets/steam-gaming-settings.svg
+Terminal=false
+Categories=Game;Settings;
+EOF
+command -v update-desktop-database >/dev/null && update-desktop-database "$APPS" 2>/dev/null || true
+
+say "Starting Steamify..."
+setsid "$DEST/ui/steamify-ui" >/dev/null 2>&1 < /dev/null &