feat: add boolean shape ops, visual undo tree, and Augmented Canvas branding

- Boolean operations (union, intersection, difference, xor) via i_overlay
  with Path shape rendering using earcutr triangulation
- Visual undo tree with branching history, checkout, and fork (Cmd+H)
  using Arc-based snapshots for structural sharing
- Consistent Augmented Canvas branding across app title, MCP server,
  CLI help text, and error messages
- macOS .app bundle script and Info.plist for Finder integration
- New MCP tool: boolean_op for agent-driven shape composition
- 26 tests passing (5 boolean, 6 history, 15 existing)

scripts/bundle-macos.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+#
+# Bundle agcanvas as a macOS .app for Finder.
+# Works on both Apple Silicon and Intel.
+#
+# Usage:
+#   ./scripts/bundle-macos.sh           # Build release + bundle
+#   ./scripts/bundle-macos.sh --install  # Also copy to /Applications
+#
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
+APP_NAME="Augmented Canvas"
+BUNDLE_DIR="$PROJECT_ROOT/target/release/bundle"
+APP_BUNDLE="$BUNDLE_DIR/$APP_NAME.app"
+
+echo "==> Building agcanvas (release)..."
+cargo build --release -p agcanvas --manifest-path "$PROJECT_ROOT/Cargo.toml"
+
+echo "==> Creating $APP_NAME.app bundle..."
+rm -rf "$APP_BUNDLE"
+mkdir -p "$APP_BUNDLE/Contents/MacOS"
+mkdir -p "$APP_BUNDLE/Contents/Resources"
+
+cp "$PROJECT_ROOT/target/release/agcanvas" "$APP_BUNDLE/Contents/MacOS/agcanvas"
+cp "$PROJECT_ROOT/assets/Info.plist" "$APP_BUNDLE/Contents/Info.plist"
+
+if [ -f "$PROJECT_ROOT/assets/AppIcon.icns" ]; then
+    cp "$PROJECT_ROOT/assets/AppIcon.icns" "$APP_BUNDLE/Contents/Resources/AppIcon.icns"
+    echo "    Icon: AppIcon.icns"
+else
+    echo "    Icon: none (add assets/AppIcon.icns for a custom icon)"
+fi
+
+printf 'APPL????' > "$APP_BUNDLE/Contents/PkgInfo"
+
+echo "==> Bundle created: $APP_BUNDLE"
+
+if [[ "${1:-}" == "--install" ]]; then
+    echo "==> Installing to /Applications..."
+    rm -rf "/Applications/$APP_NAME.app"
+    cp -r "$APP_BUNDLE" "/Applications/$APP_NAME.app"
+    echo "==> Installed: /Applications/$APP_NAME.app"
+    echo "    Open Finder → Applications → Augmented Canvas"
+fi
+
+echo "==> Done."