feat(commands): add /essay-outline command

Transforms a brain dump into a story-structured essay outline.
Pressure tests for a real thesis, applies the Saunders framework
via story-lens skill to validate hook, escalation, and conclusion,
then writes a tight outline to file.

Also fixes stale skill count in README (22 → 24).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.claude-plugin/marketplace.json

@@ -11,8 +11,8 @@
   "plugins": [
     {
       "name": "compound-engineering",
-      "description": "AI-powered development tools that get smarter with every use. Make each unit of engineering work easier than the last. Includes 25 specialized agents, 23 commands, and 22 skills.",
-      "version": "2.36.0",
+      "description": "AI-powered development tools that get smarter with every use. Make each unit of engineering work easier than the last. Includes 25 specialized agents, 24 commands, and 24 skills.",
+      "version": "2.38.0",
       "author": {
         "name": "Kieran Klaassen",
         "url": "https://github.com/kieranklaassen",