feat: add shell installer script

curl -sSL https://raw.githubusercontent.com/flashcatcloud/flashduty-cli/main/install.sh | sh

- Auto-detects OS (Linux/macOS/Windows) and architecture (x86_64/arm64)
- Auto-resolves latest version via GitHub API, or set FLASHDUTY_VERSION
- Configurable install dir via FLASHDUTY_INSTALL_DIR (default /usr/local/bin)
- Installs binary as 'flashduty' for convenience
- Handles sudo automatically when install dir is not writable

Author: debidong

install.sh

@@ -0,0 +1,120 @@
+#!/bin/sh
+# Flashduty CLI installer
+# Usage: curl -sSL https://raw.githubusercontent.com/flashcatcloud/flashduty-cli/main/install.sh | sh
+set -e
+
+REPO="flashcatcloud/flashduty-cli"
+BINARY="flashduty-cli"
+INSTALLED_NAME="flashduty"
+INSTALL_DIR="${FLASHDUTY_INSTALL_DIR:-/usr/local/bin}"
+
+# --- helper functions ---
+
+fail() {
+    printf "Error: %s\n" "$1" >&2
+    exit 1
+}
+
+info() {
+    printf "[flashduty] %s\n" "$1"
+}
+
+need_cmd() {
+    if ! command -v "$1" > /dev/null 2>&1; then
+        fail "need '$1' (command not found)"
+    fi
+}
+
+# --- detect platform ---
+
+detect_os() {
+    case "$(uname -s)" in
+        Linux*)  echo "Linux" ;;
+        Darwin*) echo "Darwin" ;;
+        MINGW*|MSYS*|CYGWIN*) echo "Windows" ;;
+        *) fail "unsupported OS: $(uname -s)" ;;
+    esac
+}
+
+detect_arch() {
+    case "$(uname -m)" in
+        x86_64|amd64)  echo "x86_64" ;;
+        aarch64|arm64) echo "arm64" ;;
+        *) fail "unsupported architecture: $(uname -m)" ;;
+    esac
+}
+
+# --- resolve version ---
+
+resolve_version() {
+    if [ -n "${FLASHDUTY_VERSION}" ]; then
+        echo "${FLASHDUTY_VERSION}"
+        return
+    fi
+    need_cmd curl
+    # Use the GitHub API to get the latest release tag
+    version=$(curl -sL "https://api.github.com/repos/${REPO}/releases/latest" \
+        | grep '"tag_name"' \
+        | sed -E 's/.*"tag_name": *"([^"]+)".*/\1/')
+    if [ -z "${version}" ]; then
+        fail "could not determine latest version. Set FLASHDUTY_VERSION to install a specific version."
+    fi
+    echo "${version}"
+}
+
+# --- main ---
+
+main() {
+    need_cmd uname
+    need_cmd tar
+    need_cmd curl
+
+    OS=$(detect_os)
+    ARCH=$(detect_arch)
+    VERSION=$(resolve_version)
+
+    if [ "${OS}" = "Windows" ]; then
+        EXT="zip"
+        need_cmd unzip
+    else
+        EXT="tar.gz"
+    fi
+
+    ARCHIVE="flashduty-cli_${OS}_${ARCH}.${EXT}"
+    URL="https://github.com/${REPO}/releases/download/${VERSION}/${ARCHIVE}"
+
+    info "Installing Flashduty CLI ${VERSION} (${OS}/${ARCH})"
+    info "Downloading ${URL}"
+
+    TMP_DIR=$(mktemp -d)
+    trap 'rm -rf "${TMP_DIR}"' EXIT
+
+    HTTP_CODE=$(curl -sL -H "Accept: application/octet-stream" -o "${TMP_DIR}/${ARCHIVE}" -w "%{http_code}" "${URL}")
+    if [ "${HTTP_CODE}" != "200" ]; then
+        fail "download failed (HTTP ${HTTP_CODE}). Check that ${VERSION} exists at https://github.com/${REPO}/releases"
+    fi
+
+    if [ "${EXT}" = "zip" ]; then
+        unzip -q "${TMP_DIR}/${ARCHIVE}" -d "${TMP_DIR}"
+    else
+        tar xzf "${TMP_DIR}/${ARCHIVE}" -C "${TMP_DIR}"
+    fi
+
+    if [ ! -f "${TMP_DIR}/${BINARY}" ]; then
+        fail "binary '${BINARY}' not found in archive"
+    fi
+
+    # Install (rename flashduty-cli -> flashduty for convenience)
+    if [ -w "${INSTALL_DIR}" ]; then
+        mv "${TMP_DIR}/${BINARY}" "${INSTALL_DIR}/${INSTALLED_NAME}"
+    else
+        info "Need elevated permissions to install to ${INSTALL_DIR}"
+        sudo mv "${TMP_DIR}/${BINARY}" "${INSTALL_DIR}/${INSTALLED_NAME}"
+    fi
+    chmod +x "${INSTALL_DIR}/${INSTALLED_NAME}"
+
+    info "Installed to ${INSTALL_DIR}/${INSTALLED_NAME}"
+    info "Run 'flashduty version' to verify"
+}
+
+main