chore: align plugin manifest with Cursor examples

Declare the rules directory in plugin.json and enforce it in validation so the package layout matches Cursor's published plugin patterns.

Made-with: Cursor

Author: jesseoue

.cursor-plugin/plugin.json

@@ -32,6 +32,7 @@
     "mcp",
     "api"
   ],
+  "rules": "./rules/",
   "skills": "./skills/",
   "mcpServers": "./mcp.json"
 }

scripts/validate-plugin.mjs

@@ -57,6 +57,10 @@ try {
 		plugin.skills === "./skills/",
 		"Plugin must expose the skills directory with an explicit relative path",
 	);
+	assert(
+		plugin.rules === "./rules/",
+		"Plugin must expose the rules directory with an explicit relative path",
+	);
 	assert(exists(plugin.logo), `Missing logo file: ${plugin.logo}`);
 
 	assert(