feat: add uninstall scripts for X11 and macOS

scripts/uninstall-linux-x11.sh — strips ahfail from common PAM service
files and removes binaries (via ninja uninstall or known paths).

scripts/uninstall-macos.sh — strips ahfail from screensaverui/screensaver
and removes /usr/local/lib/ahfail/.

README: add Uninstall section covering all four cases (X11, Wayland,
Homebrew macOS, manual macOS).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/uninstall-linux-x11.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# uninstall-linux-x11.sh — remove ahfail PAM module from X11 screen lockers
+# Run from the repository root (uses ninja uninstall if builddir is present).
+set -euo pipefail
+
+BOLD=$(tput bold 2>/dev/null || true)
+RESET=$(tput sgr0 2>/dev/null || true)
+
+step() { echo "${BOLD}==> $*${RESET}"; }
+
+[[ "$(uname)" == "Linux" ]] || { echo "This script is for Linux only." >&2; exit 1; }
+
+# ── 1. Remove PAM config lines ────────────────────────────────────────────────
+step "Removing ahfail from PAM service files..."
+removed_pam=0
+for pam_file in /etc/pam.d/i3lock /etc/pam.d/xscreensaver /etc/pam.d/lightdm \
+                /etc/pam.d/gdm /etc/pam.d/sddm /etc/pam.d/gtklock; do
+    if [[ -f "$pam_file" ]] && grep -q "ahfail" "$pam_file"; then
+        echo "  Patching ${pam_file}..."
+        sudo sed -i '/ahfail/d' "$pam_file"
+        removed_pam=1
+    fi
+done
+[[ $removed_pam -eq 0 ]] && echo "  No ahfail PAM entries found in common service files."
+
+# ── 2. Remove installed files ─────────────────────────────────────────────────
+step "Removing installed files..."
+
+# Prefer meson's own uninstall if the builddir is still present
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+BUILDDIR="${SCRIPT_DIR}/../builddir"
+if [[ -f "${BUILDDIR}/build.ninja" ]]; then
+    echo "  Running meson uninstall..."
+    sudo ninja -C "$BUILDDIR" uninstall
+else
+    echo "  builddir not found — removing known paths manually..."
+    for dir in /usr/lib/ahfail /usr/local/lib/ahfail \
+                /usr/lib64/ahfail /usr/lib/x86_64-linux-gnu/ahfail; do
+        if [[ -d "$dir" ]]; then
+            sudo rm -rf "$dir"
+            echo "  Removed ${dir}."
+        fi
+    done
+    for f in /usr/lib/gtklock/ahfail-module.so \
+              /usr/local/lib/gtklock/ahfail-module.so; do
+        if [[ -f "$f" ]]; then
+            sudo rm -f "$f"
+            echo "  Removed ${f}."
+        fi
+    done
+fi
+
+echo ""
+echo "${BOLD}Done.${RESET}"

scripts/uninstall-macos.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+# uninstall-macos.sh — remove ahfail from macOS (manual/script install)
+# For Homebrew installs: brew uninstall ahfail, then run this to clean up PAM.
+set -euo pipefail
+
+INSTALL_DIR="/usr/local/lib/ahfail"
+BOLD=$(tput bold 2>/dev/null || true)
+RESET=$(tput sgr0 2>/dev/null || true)
+
+step() { echo "${BOLD}==> $*${RESET}"; }
+
+[[ "$(uname)" == "Darwin" ]] || { echo "This script is for macOS only." >&2; exit 1; }
+
+# ── 1. Remove PAM config line ─────────────────────────────────────────────────
+step "Removing ahfail from PAM configuration..."
+removed_pam=0
+for pam_file in /etc/pam.d/screensaverui /etc/pam.d/screensaver; do
+    if [[ -f "$pam_file" ]] && grep -q "ahfail" "$pam_file"; then
+        echo "  Patching ${pam_file}..."
+        sudo sed -i '' '/ahfail/d' "$pam_file"
+        removed_pam=1
+    fi
+done
+[[ $removed_pam -eq 0 ]] && echo "  No ahfail PAM entries found."
+
+# ── 2. Remove binaries ────────────────────────────────────────────────────────
+step "Removing binaries..."
+if [[ -d "$INSTALL_DIR" ]]; then
+    sudo rm -rf "$INSTALL_DIR"
+    echo "  Removed ${INSTALL_DIR}."
+else
+    echo "  ${INSTALL_DIR} not found — skipping."
+fi
+
+echo ""
+echo "${BOLD}Done.${RESET}"