Add run.sh to install Flutter desktop deps and launch the app

Provides a one-command setup for Arch Linux (builds flutter-bin from
the AUR via makepkg) and Ubuntu/Debian (apt if a flutter package
exists, otherwise the upstream SDK clone), plus the Linux desktop
build toolchain, then runs `flutter run -d linux`.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

run.sh

@@ -0,0 +1,129 @@
+#!/bin/bash
+#
+# run.sh — install missing Flutter + Linux-desktop build dependencies, then
+# launch the todo app on Arch Linux or Ubuntu/Debian.
+#
+# Usage: ./run.sh
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+readonly SCRIPT_DIR
+readonly AUR_FLUTTER_BIN_URL="https://aur.archlinux.org/flutter-bin.git"
+
+BUILD_DIR=""
+cleanup() {
+    if [[ -n "${BUILD_DIR}" && -d "${BUILD_DIR}" ]]; then
+        rm -rf "${BUILD_DIR}"
+    fi
+}
+trap cleanup EXIT
+
+log() { printf '==> %s\n' "$1"; }
+err() { printf 'error: %s\n' "$1" >&2; }
+
+# Echoes "arch" or "debian" depending on /etc/os-release; exits otherwise.
+detect_distro() {
+    if [[ -f /etc/os-release ]]; then
+        # shellcheck disable=SC1091
+        source /etc/os-release
+        case "${ID:-}:${ID_LIKE:-}" in
+            *arch*) echo "arch"; return ;;
+            *debian*|*ubuntu*) echo "debian"; return ;;
+        esac
+    fi
+    err "unsupported distro (expected Arch Linux or Ubuntu/Debian)"
+    exit 1
+}
+
+require_non_root() {
+    if [[ "${EUID}" -eq 0 ]]; then
+        err "run as a regular user with sudo access, not as root (makepkg/apt need that)"
+        exit 1
+    fi
+}
+
+# makepkg refuses to run as root, so flutter-bin is built directly from its
+# AUR git repo rather than requiring an AUR helper (yay/paru) to be installed.
+install_flutter_arch() {
+    command -v flutter >/dev/null 2>&1 && return
+    log "flutter not found; building flutter-bin from the AUR"
+    sudo pacman -S --needed --noconfirm base-devel git
+    BUILD_DIR="$(mktemp -d)"
+    git clone --depth 1 "${AUR_FLUTTER_BIN_URL}" "${BUILD_DIR}/flutter-bin"
+    (cd "${BUILD_DIR}/flutter-bin" && makepkg -si --noconfirm)
+}
+
+install_linux_desktop_deps_arch() {
+    local -a pkgs=(clang cmake ninja pkgconf gtk3)
+    local -a missing=()
+    for pkg in "${pkgs[@]}"; do
+        pacman -Qi "${pkg}" >/dev/null 2>&1 || missing+=("${pkg}")
+    done
+    if ((${#missing[@]} > 0)); then
+        log "installing missing build deps: ${missing[*]}"
+        sudo pacman -S --needed --noconfirm "${missing[@]}"
+    fi
+}
+
+# Prefers a real apt package if the user's mirrors happen to carry one;
+# Ubuntu/Debian have none in the standard repos as of writing, so this
+# normally falls back to cloning the upstream Flutter SDK.
+install_flutter_debian() {
+    command -v flutter >/dev/null 2>&1 && return
+    log "flutter not found; checking apt for a flutter package"
+    sudo apt-get update -qq
+    if apt-cache show flutter >/dev/null 2>&1; then
+        sudo apt-get install -y flutter
+        return
+    fi
+    log "no apt package named 'flutter'; cloning the Flutter SDK instead"
+    local install_dir="${HOME}/development/flutter"
+    if [[ ! -d "${install_dir}" ]]; then
+        sudo apt-get install -y git curl
+        git clone --depth 1 -b stable https://github.com/flutter/flutter.git "${install_dir}"
+    fi
+    export PATH="${install_dir}/bin:${PATH}"
+    log "flutter installed at ${install_dir}; add 'export PATH=\"${install_dir}/bin:\$PATH\"' to your shell rc to make this permanent"
+}
+
+install_linux_desktop_deps_debian() {
+    local -a pkgs=(clang cmake ninja-build pkg-config libgtk-3-dev liblzma-dev)
+    local -a missing=()
+    for pkg in "${pkgs[@]}"; do
+        dpkg -s "${pkg}" >/dev/null 2>&1 || missing+=("${pkg}")
+    done
+    if ((${#missing[@]} > 0)); then
+        log "installing missing build deps: ${missing[*]}"
+        sudo apt-get update -qq
+        sudo apt-get install -y "${missing[@]}"
+    fi
+}
+
+main() {
+    require_non_root
+    local distro
+    distro="$(detect_distro)"
+
+    case "${distro}" in
+        arch)
+            install_flutter_arch
+            install_linux_desktop_deps_arch
+            ;;
+        debian)
+            install_flutter_debian
+            install_linux_desktop_deps_debian
+            ;;
+    esac
+
+    command -v flutter >/dev/null 2>&1 || { err "flutter still not on PATH after install"; exit 1; }
+
+    cd "${SCRIPT_DIR}"
+    flutter config --enable-linux-desktop >/dev/null
+    log "fetching pub packages"
+    flutter pub get
+    log "launching the app"
+    exec flutter run -d linux
+}
+
+main "$@"