feat(payload-ai): implement context-aware Payload CMS Agent

- ChatWindow now gathers page context (URL, collectionSlug, document ID)
- chatEndpoint fetches real AIChatPermissions from database
- Agent uses OpenRouter Gemini 3 Flash with maxSteps: 10 for autonomous multi-step tool execution
- Fallback default collections when no permissions configured

packages/payload-ai/src/components/ChatWindow/index.tsx

@@ -1,6 +1,6 @@
 'use client'
 
-import React, { useState } from 'react'
+import React, { useState, useEffect } from 'react'
 import { useChat } from '@ai-sdk/react'
 import './ChatWindow.scss'
 
@@ -15,10 +15,38 @@ export const ChatWindowProvider: React.FC<{ children: React.ReactNode }> = ({ ch
 
 const ChatWindow: React.FC = () => {
     const [isOpen, setIsOpen] = useState(false)
+    const [pageContext, setPageContext] = useState<any>({ url: '' })
+
+    useEffect(() => {
+        if (typeof window !== 'undefined') {
+            const path = window.location.pathname;
+            let collectionSlug = null;
+            let id = null;
+            // Payload admin URLs are usually /admin/collections/:slug/:id
+            const match = path.match(/\/collections\/([^/]+)(?:\/([^/]+))?/);
+            if (match) {
+                collectionSlug = match[1];
+                if (match[2] && match[2] !== 'create') {
+                    id = match[2];
+                }
+            }
+
+            setPageContext({
+                url: window.location.href,
+                title: document.title,
+                collectionSlug,
+                id
+            })
+        }
+    }, [isOpen]) // Refresh context when chat is opened
+
     // @ts-ignore - AI hook version mismatch between core and react packages
     const { messages, input, handleInputChange, handleSubmit, setMessages } = useChat({
         api: '/api/mcp-chat',
-        initialMessages: []
+        initialMessages: [],
+        body: {
+            pageContext
+        }
     } as any)
 
     // Basic implementation to toggle chat window and submit messages
@@ -51,8 +79,8 @@ const ChatWindow: React.FC = () => {
                         position: 'fixed',
                         bottom: '80px',
                         right: '20px',
-                        width: '400px',
-                        height: '600px',
+                        width: '450px',
+                        height: '650px',
                         backgroundColor: '#fff',
                         border: '1px solid #eaeaea',
                         borderRadius: '12px',