add macOS uninstall script (#276)

Co-authored-by: Abhisek Datta <abhisek.datta@gmail.com>

scripts/pmg_uninstall_macos.sh

@@ -0,0 +1,56 @@
+#!/bin/bash
+# pmg_uninstall_macos.sh — Uninstall PMG, remove config, aliases, shims, and cloud credentials.
+#
+# This script is intended to be deployed via Jamf or similar MDM tools.
+#
+# Usage:
+#   ./pmg_uninstall_macos.sh
+#
+# What it does:
+#   1. Removes PMG config, shell aliases, and PATH shims
+#   2. Clears cloud credentials from macOS Keychain
+#   3. Uninstalls the pmg binary (via Homebrew or direct removal)
+
+set -euo pipefail
+
+if [[ "$(uname -s)" != "Darwin" ]]; then
+  echo "Error: this script is for macOS only" >&2
+  exit 1
+fi
+
+log() { echo "==> $*"; }
+
+# ── Remove config, aliases, and shims ────────────────────────────────────────
+if command -v pmg &>/dev/null; then
+  log "Removing PMG config, aliases, and shims"
+  pmg setup remove --config-file || true
+
+  log "Clearing cloud credentials from keychain"
+  pmg cloud logout || true
+fi
+
+# ── Uninstall pmg binary ────────────────────────────────────────────────────
+BREW_BIN=""
+for candidate in "/opt/homebrew/bin/brew" "/usr/local/bin/brew"; do
+  if [[ -x "$candidate" ]]; then
+    BREW_BIN="$candidate"
+    break
+  fi
+done
+
+if [[ -n "$BREW_BIN" ]] && "$BREW_BIN" ls --versions safedep/tap/pmg &>/dev/null; then
+  log "Uninstalling pmg via Homebrew"
+  "$BREW_BIN" uninstall safedep/tap/pmg
+else
+  log "Removing pmg binary"
+  if [[ -f "/usr/local/bin/pmg" ]]; then
+    if [[ -w "/usr/local/bin/pmg" ]]; then
+      rm -f "/usr/local/bin/pmg"
+    else
+      sudo rm -f "/usr/local/bin/pmg"
+    fi
+  fi
+fi
+
+# ── Done ─────────────────────────────────────────────────────────────────────
+log "pmg uninstall complete!"