Bump version to 0.2.0 (first React-based release)

v0.1.0 was the Svelte version, preserved on branch svelte-archive.
v0.2.0 marks the React rewrite: same features, dramatically more
reliable interactions (no more fighting prop reactivity through the
recursive Pane chain), plus scrollbar theming and the global
broadcast toggle in the titlebar.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "tiletopia",
   "private": true,
-  "version": "0.1.0",
+  "version": "0.2.0",
   "type": "module",
   "scripts": {
     "dev": "vite",