Rename /codify to /compound and codify-docs to compound-docs

The new names better reflect the compounding engineering philosophy:
each documented solution compounds your team's knowledge.

- /codify → /compound (old command shows deprecation notice)
- codify-docs → compound-docs skill
- Updated all docs, philosophy sections, and references

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

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

plugins/compounding-engineering/.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "compounding-engineering",
-  "version": "2.6.2",
+  "version": "2.7.0",
   "description": "AI-powered development tools. 23 agents, 16 commands, 11 skills, 2 MCP servers for code review, research, design, and workflow automation.",
   "author": {
     "name": "Kieran Klaassen",