refactor: Update agent-sdk-dev plugin structure and configuration (#9230)

- Move plugin.json to .claude-plugin directory to match pr-review-toolkit pattern
- Add author information: Ashwin Bhat (ashwin@anthropic.com)
- Update model field from sonnet-4.5 to sonnet in all agent/command definitions

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

Co-authored-by: Claude <noreply@anthropic.com>

plugins/agent-sdk-dev/.claude-plugin/plugin.json

@@ -0,0 +1,9 @@
+{
+  "name": "agent-sdk-dev",
+  "description": "Claude Agent SDK Development Plugin",
+  "version": "1.0.0",
+  "author": {
+    "name": "Ashwin Bhat",
+    "email": "ashwin@anthropic.com"
+  }
+}

plugins/agent-sdk-dev/agents/agent-sdk-verifier-py.md

@@ -1,7 +1,7 @@
 ---
 name: agent-sdk-verifier-py
 description: Use this agent to verify that a Python Agent SDK application is properly configured, follows SDK best practices and documentation recommendations, and is ready for deployment or testing. This agent should be invoked after a Python Agent SDK app has been created or modified.
-model: sonnet-4.5
+model: sonnet
 ---
 
 You are a Python Agent SDK application verifier. Your role is to thoroughly inspect Python Agent SDK applications for correct SDK usage, adherence to official documentation recommendations, and readiness for deployment.

plugins/agent-sdk-dev/agents/agent-sdk-verifier-ts.md

@@ -1,7 +1,7 @@
 ---
 name: agent-sdk-verifier-ts
 description: Use this agent to verify that a TypeScript Agent SDK application is properly configured, follows SDK best practices and documentation recommendations, and is ready for deployment or testing. This agent should be invoked after a TypeScript Agent SDK app has been created or modified.
-model: sonnet-4.5
+model: sonnet
 ---
 
 You are a TypeScript Agent SDK application verifier. Your role is to thoroughly inspect TypeScript Agent SDK applications for correct SDK usage, adherence to official documentation recommendations, and readiness for deployment.

plugins/agent-sdk-dev/commands/new-sdk-app.md

@@ -1,7 +1,7 @@
 ---
 description: Create and setup a new Claude Agent SDK application
 argument-hint: [project-name]
-model: sonnet-4.5
+model: sonnet
 ---
 
 You are tasked with helping the user create a new Claude Agent SDK application. Follow these steps carefully:

plugins/agent-sdk-dev/plugin.json

@@ -1,5 +0,0 @@
-{
-  "name": "agent-sdk-dev",
-  "description": "Claude Agent SDK Development Plugin",
-  "version": "1.0.0"
-}