Add catch-all email group and platform filtering (#3)

- Add catch-all email group with admin-adam@modelcontextprotocol.io
- Add onlyOnPlatforms configuration to restrict groups to specific platforms
- Set antitrust and catch-all groups to Google only
- Groups default to all platforms when onlyOnPlatforms is not specified

src/config/users.ts

@@ -6,6 +6,10 @@ export const MEMBERS: readonly Member[] = [
     email: 'adam@modelcontextprotocol.io',
     memberOf: ['test-child'],
   },
+  {
+    email: 'adamj@anthropic.com',
+    memberOf: ['catch-all'],
+  },
   {
     email: 'davidsp@anthropic.com',
     memberOf: ['antitrust'],