Remove agents/commands fields from plugin.json

Since agents and commands are in default directories (./agents/ and ./commands/), they should be auto-discovered by Claude Code without explicit path declarations in plugin.json.

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

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

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

@@ -17,7 +17,5 @@
     "code-review",
     "quality",
     "knowledge-management"
-  ],
+  ]
-  "agents": "./agents/",
-  "commands": "./commands/"
 }