Initial scaffold: idempotent Sunshine + Moonlight installer for Omarchy

Sets up bidirectional game streaming across Omarchy/Hyprland/Wayland
machines (NVIDIA desktop and AMD Framework laptop), with the Macbook
as an additional Moonlight client.

The same install.sh runs on either machine; GPU vendor is detected at
runtime and the appropriate hardware-encode packages are installed.

Includes:
- KMS capture setup (cap_sys_admin on sunshine, input group, uinput udev rule)
- ufw / firewalld port opening when a firewall is active
- systemd --user service + loginctl enable-linger for always-on hosting
- uninstall.sh with --purge for user data removal
- Flags to install host-only or client-only

lib/common.sh

@@ -0,0 +1,62 @@
+#!/usr/bin/env bash
+# Shared helpers: logging, sudo, preflight checks, idempotency primitives.
+
+if [[ -t 1 ]]; then
+  BOLD=$'\033[1m'
+  DIM=$'\033[2m'
+  RED=$'\033[31m'
+  GREEN=$'\033[32m'
+  YELLOW=$'\033[33m'
+  BLUE=$'\033[34m'
+  RESET=$'\033[0m'
+else
+  BOLD="" DIM="" RED="" GREEN="" YELLOW="" BLUE="" RESET=""
+fi
+
+step() { printf '\n%s==>%s %s%s%s\n' "$BLUE" "$RESET" "$BOLD" "$*" "$RESET"; }
+info() { printf '  %s\n' "$*"; }
+ok()   { printf '  %s✓%s %s\n' "$GREEN" "$RESET" "$*"; }
+warn() { printf '  %s!%s %s\n' "$YELLOW" "$RESET" "$*" >&2; }
+err()  { printf '  %s✗%s %s\n' "$RED" "$RESET" "$*" >&2; }
+
+# Run as root via sudo, preserving prompt visibility.
+as_root() { sudo "$@"; }
+
+require_not_root() {
+  if [[ $EUID -eq 0 ]]; then
+    err "Do not run this script as root. It will sudo where needed."
+    exit 1
+  fi
+}
+
+require_arch() {
+  if [[ ! -f /etc/arch-release ]] && ! grep -q '^ID=arch' /etc/os-release 2>/dev/null; then
+    err "This script targets Arch Linux (Omarchy). /etc/arch-release not found."
+    exit 1
+  fi
+}
+
+require_yay() {
+  if ! command -v yay >/dev/null 2>&1; then
+    err "yay is required to install AUR packages. Install yay first."
+    exit 1
+  fi
+}
+
+# True if package is installed (pacman -Qi).
+pkg_installed() { pacman -Qi "$1" >/dev/null 2>&1; }
+
+# Install one or more packages via yay if any are missing.
+yay_install() {
+  local missing=()
+  local p
+  for p in "$@"; do
+    pkg_installed "$p" || missing+=("$p")
+  done
+  if [[ ${#missing[@]} -eq 0 ]]; then
+    ok "Already installed: $*"
+    return 0
+  fi
+  info "Installing: ${missing[*]}"
+  yay -S --needed --noconfirm "${missing[@]}"
+}