docs: Add ObjectQL Plugin quick reference guide

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

OBJECTQL_PLUGIN_QUICKSTART.md

@@ -0,0 +1,225 @@
+# ObjectQL Plugin - Quick Reference
+
+## Installation
+
+```bash
+npm install @objectstack/runtime
+```
+
+## Basic Usage
+
+### Default ObjectQL (Recommended)
+
+```typescript
+import { ObjectStackKernel, ObjectQLPlugin } from '@objectstack/runtime';
+
+const kernel = new ObjectStackKernel([
+  new ObjectQLPlugin(),
+  // ... other plugins
+]);
+
+await kernel.start();
+```
+
+### Custom ObjectQL Instance
+
+```typescript
+import { ObjectStackKernel, ObjectQLPlugin, ObjectQL } from '@objectstack/runtime';
+
+// Create custom instance
+const customQL = new ObjectQL({ 
+  env: 'production',
+  // custom options
+});
+
+// Configure as needed
+customQL.registerHook('beforeInsert', async (ctx) => {
+  console.log(`Inserting into ${ctx.object}`);
+});
+
+// Use in kernel
+const kernel = new ObjectStackKernel([
+  new ObjectQLPlugin(customQL),
+  // ... other plugins
+]);
+
+await kernel.start();
+```
+
+### Backward Compatible (Legacy)
+
+```typescript
+// Still works without ObjectQLPlugin, but shows warning
+const kernel = new ObjectStackKernel([
+  // ... plugins
+]);
+```
+
+## API Reference
+
+### ObjectQLPlugin Constructor
+
+```typescript
+new ObjectQLPlugin(ql?: ObjectQL, hostContext?: Record<string, any>)
+```
+
+**Parameters:**
+- `ql` (optional): Custom ObjectQL instance to use
+- `hostContext` (optional): Configuration for new ObjectQL instance (ignored if `ql` provided)
+
+**Note:** If both parameters are provided, `hostContext` is ignored with a warning.
+
+### Examples
+
+```typescript
+// Create with default settings
+new ObjectQLPlugin()
+
+// Use custom instance
+const custom = new ObjectQL({ env: 'prod' });
+new ObjectQLPlugin(custom)
+
+// Create with custom context
+new ObjectQLPlugin(undefined, { env: 'prod', debug: true })
+```
+
+## Migration Guide
+
+### From Hardcoded to Plugin-Based
+
+**Before:**
+```typescript
+const kernel = new ObjectStackKernel([appConfig, driver]);
+```
+
+**After:**
+```typescript
+const kernel = new ObjectStackKernel([
+  new ObjectQLPlugin(),  // Add this line
+  appConfig,
+  driver
+]);
+```
+
+## Common Patterns
+
+### Testing with Mock ObjectQL
+
+```typescript
+import { ObjectQLPlugin } from '@objectstack/runtime';
+import { MockObjectQL } from './mocks';
+
+const mockQL = new MockObjectQL();
+const kernel = new ObjectStackKernel([
+  new ObjectQLPlugin(mockQL),
+  // ... test config
+]);
+```
+
+### Multiple Environments
+
+```typescript
+// Production
+const prodQL = new ObjectQL({ env: 'production', cache: true });
+const prodKernel = new ObjectStackKernel([
+  new ObjectQLPlugin(prodQL),
+  // ... production plugins
+]);
+
+// Development
+const devKernel = new ObjectStackKernel([
+  new ObjectQLPlugin(undefined, { env: 'development', debug: true }),
+  // ... dev plugins
+]);
+```
+
+### Custom ObjectQL from Separate Project
+
+```typescript
+// Your custom implementation
+import { MyCustomObjectQL } from '@mycompany/custom-objectql';
+
+const customQL = new MyCustomObjectQL({
+  specialFeature: true,
+  // custom options
+});
+
+const kernel = new ObjectStackKernel([
+  new ObjectQLPlugin(customQL),
+  // ... other plugins
+]);
+```
+
+## Troubleshooting
+
+### Error: "ObjectQL engine not initialized"
+
+This means the kernel tried to use ObjectQL before it was set up. Make sure:
+1. You include `ObjectQLPlugin` in your plugins array, OR
+2. The kernel has backward compatibility enabled
+
+### Warning: "No ObjectQL plugin found..."
+
+This is a deprecation warning. Your code will work, but consider migrating to:
+
+```typescript
+new ObjectStackKernel([
+  new ObjectQLPlugin(),  // Add this
+  // ... other plugins
+]);
+```
+
+### Warning: "Both ql and hostContext provided..."
+
+You passed both a custom ObjectQL instance and host context:
+
+```typescript
+// ❌ Don't do this
+new ObjectQLPlugin(customQL, { env: 'prod' })  // hostContext ignored
+
+// ✅ Do this instead
+new ObjectQLPlugin(customQL)  // Use custom instance
+
+// ✅ Or this
+new ObjectQLPlugin(undefined, { env: 'prod' })  // Create with context
+```
+
+## Advanced
+
+### Symbol-Based Detection
+
+ObjectQLPlugin uses a symbol for reliable detection:
+
+```typescript
+import { OBJECTQL_PLUGIN_MARKER } from '@objectstack/runtime';
+
+// Check if a plugin is an ObjectQL plugin
+const isObjectQLPlugin = OBJECTQL_PLUGIN_MARKER in plugin;
+```
+
+### Type Safety
+
+The kernel's `ql` property is typed as optional:
+
+```typescript
+export class ObjectStackKernel {
+  public ql?: ObjectQL;
+  
+  private ensureObjectQL(): ObjectQL {
+    if (!this.ql) {
+      throw new Error('ObjectQL engine not initialized');
+    }
+    return this.ql;
+  }
+}
+```
+
+## Resources
+
+- [Full Documentation](./packages/runtime/README.md)
+- [Implementation Summary](./OBJECTQL_PLUGIN_SUMMARY.md)
+- [Custom ObjectQL Example](./examples/custom-objectql-example.ts)
+
+## License
+
+Apache-2.0