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)

assets/Info.plist

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <key>CFBundleName</key>
+    <string>Augmented Canvas</string>
+    <key>CFBundleDisplayName</key>
+    <string>Augmented Canvas</string>
+    <key>CFBundleIdentifier</key>
+    <string>com.agcanvas.app</string>
+    <key>CFBundleVersion</key>
+    <string>0.1.0</string>
+    <key>CFBundleShortVersionString</key>
+    <string>0.1.0</string>
+    <key>CFBundlePackageType</key>
+    <string>APPL</string>
+    <key>CFBundleExecutable</key>
+    <string>agcanvas</string>
+    <key>CFBundleIconFile</key>
+    <string>AppIcon</string>
+    <key>LSMinimumSystemVersion</key>
+    <string>11.0</string>
+    <key>NSHighResolutionCapable</key>
+    <true/>
+    <key>NSSupportsAutomaticGraphicsSwitching</key>
+    <true/>
+    <key>CFBundleInfoDictionaryVersion</key>
+    <string>6.0</string>
+    <key>LSApplicationCategoryType</key>
+    <string>public.app-category.developer-tools</string>
+</dict>
+</plist>