chore: bump version to 0.2.3, add CLAUDE.md

Add CLAUDE.md with release checklist and build notes.
Bump version for new release with ABI fix, Windows path fix,
x64 macOS support, and Extensions scroll fix.

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "codepilot",
-  "version": "0.2.2",
+  "version": "0.2.3",
   "private": true,
   "main": "dist-electron/main.js",
   "scripts": {