chore(cdk): revert agent-plugins blueprint to krokoko/agent-plugins

The upstream blueprint at ``cdk/src/stacks/agent.ts`` points at
``krokoko/agent-plugins``. During PR aws-samples#52 deploy-validation it was
flipped to ``scoropeza/agent-plugins`` so the test stack would onboard
Sam's own fork for hands-on testing. That override leaked into an
earlier PR commit (``1c87094``) and has to come back off before push.

This commit is a pure revert of the single ``repo:`` line. Everything
else on the branch stays as-is.

Author: bgagent

cdk/src/stacks/agent.ts

@@ -95,7 +95,7 @@ export class AgentStack extends Stack {
 
     // --- Repository onboarding ---
     const agentPluginsBlueprint = new Blueprint(this, 'AgentPluginsBlueprint', {
-      repo: 'scoropeza/agent-plugins',
+      repo: 'krokoko/agent-plugins',
       repoTable: repoTable.table,
     });