chore: bump version to 4.6.0 (#72)

Bumps all four plugin manifests to 4.6.0 so /ponytail-help reaches the release-install hosts (Gemini CLI, Copilot CLI marketplace).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

gemini-extension.json

@@ -1,6 +1,6 @@
 {
   "name": "ponytail",
-  "version": "4.5.0",
+  "version": "4.6.0",
   "description": "Lazy senior dev mode. Forces the simplest, shortest solution that actually works: YAGNI, stdlib first, no unrequested abstractions.",
   "contextFileName": "AGENTS.md"
 }