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>

docs/pages/getting-started.html

@@ -335,7 +335,7 @@ claude agent git-history-analyzer "Show changes to user model"</code></pre>
 /plan
 /review 123
 /work
-/codify
+/compound
 
 # Utility commands
 /changelog