fix raycaster layers, polygon drag, slider undo, and grid events

- Enable EDITOR_LAYER on R3F raycaster for proper hit detection
- Fix polygon editor drag using refs and direct position passing
- Handle pointercancel events and fix pointerId access in polygon editor
- Fix slider undo by reverting to start value before resuming temporal state
- Allow grid:move during camera drag so polygon editor works while panning
- Bump better-auth to ^1.5.2 and turbo to ^2.8.12
- Remove explicit return type on createAuth for better inference

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

apps/editor/package.json

@@ -41,7 +41,7 @@
     "@vercel/speed-insights": "^1.3.1",
     "@vercel/toolbar": "^0.2.2",
     "@visual-json/react": "latest",
-    "better-auth": "^1.4.19",
+    "better-auth": "^1.5.2",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "howler": "^2.2.4",