docs: add macOS install script for Nucleus demo app

Allows one-line installation via:
curl -fsSL https://nucleus.kdroidfilter.com/install.sh | bash

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

Author: kdroidFilter

docs/install.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+
+set -e
+
+repo="kdroidFilter/Nucleus"
+app_name="nucleusdemo"
+
+# Resolve latest version tag from GitHub
+echo "Checking latest version ..."
+version=$(curl -sI "https://github.com/${repo}/releases/latest" | grep -i '^location:' | sed 's/.*tag\///' | tr -d '\r\n')
+
+if [ -z "$version" ]; then
+  echo "Failed to determine latest version."
+  exit 1
+fi
+
+# Strip leading 'v' for the filename (v1.1.1 -> 1.1.1)
+version_number="${version#v}"
+echo "Latest version: $version (${version_number})"
+
+arch=$(arch)
+if [[ "$arch" == "i386" ]]; then
+  mac_zip_url="https://github.com/${repo}/releases/download/${version}/${app_name}-${version_number}-mac-x64.zip"
+elif [[ "$arch" == "arm64" ]]; then
+  mac_zip_url="https://github.com/${repo}/releases/download/${version}/${app_name}-${version_number}-mac-arm64.zip"
+else
+  echo "Unsupported CPU architecture: $arch"
+  exit 1
+fi
+
+tmpdir="$(mktemp -d -t download)"
+tmpfile="$tmpdir/app.zip"
+
+cleanup() {
+  cd "$HOME" || true
+  if [ -e "$tmpfile" ]; then
+    rm -f "$tmpfile"
+  fi
+  rmdir "$tmpdir" 2>/dev/null || true
+}
+trap cleanup EXIT
+
+echo "Downloading $app_name ..."
+curl -L --output "$tmpfile" --progress-bar "$mac_zip_url"
+
+if [ -w /Applications ]; then
+  cd /Applications
+else
+  if [ ! -d "$HOME/Applications" ]; then
+    mkdir "$HOME/Applications"
+  fi
+  cd "$HOME/Applications"
+fi
+
+if [ -d "${app_name}.app" ]; then
+  echo "App folder ${app_name}.app already exists, removing."
+  rm -rf "${app_name}.app"
+fi
+
+echo "Extracting to $PWD ..."
+ditto -x -k "$tmpfile" .
+
+# Remove quarantine attribute
+if command -v xattr >/dev/null 2>&1; then
+  xattr -r -d com.apple.quarantine "${app_name}.app" 2>/dev/null || true
+fi
+
+open "${app_name}.app"
+
+cleanup
+exit 0