merge: resolve CHANGELOG conflict with main, bump to v0.13.5.0

Main landed v0.13.4.0 (Sidebar Defense) while this branch also used
v0.13.4.0 (GStack Learns). Resolved by bumping this branch to v0.13.5.0
and keeping both entries in chronological order.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "gstack",
-  "version": "0.13.4.0",
+  "version": "0.13.5.0",
   "description": "Garry's Stack — Claude Code skills + fast headless browser. One repo, one install, entire AI engineering workflow.",
   "license": "MIT",
   "type": "module",