fix: keep local kernel-factory exports, fix migration guide version and API

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

Author: Copilot

content/docs/guides/objectql-migration.mdx

@@ -26,7 +26,7 @@ All core functionality previously provided by `@objectql/core` is now available
     "dependencies": {
 -     "@objectql/core": "^4.x",
 -     "@objectql/types": "^4.x",
-+     "@objectstack/objectql": "^3.1.0"
++     "@objectstack/objectql": "^3.0.4"
     }
   }
 ```
@@ -91,7 +91,7 @@ import { createObjectQLKernel } from '@objectstack/objectql';
 const kernel = await createObjectQLKernel({
   plugins: [myDriverPlugin],
 });
-await kernel.bootstrap();
+await kernel.start();
 ```
 
 ### MetadataRegistry → MetadataFacade

packages/foundation/core/src/index.ts

@@ -13,15 +13,17 @@
 /** @deprecated Import ObjectQL from `@objectstack/objectql` instead. This bridge class will be removed in a future version. */
 export { ObjectQL, type ObjectQLConfig } from './app';
 
+// ── Convenience factory (local implementation — wraps upstream kernel) ──
+export { createObjectQLKernel } from './kernel-factory';
+export type { ObjectQLKernelOptions } from './kernel-factory';
+
 // ── Re-exports from @objectstack/objectql (deprecated — import directly from upstream) ──
 /** @deprecated Import from `@objectstack/objectql` instead. */
 export { ObjectRepository, ScopedContext, SchemaRegistry } from '@objectstack/objectql';
 /** @deprecated Import from `@objectstack/objectql` instead. */
-export { createObjectQLKernel } from '@objectstack/objectql';
-/** @deprecated Import from `@objectstack/objectql` instead. */
 export { toTitleCase, convertIntrospectedSchemaToObjects } from '@objectstack/objectql';
 /** @deprecated Import from `@objectstack/objectql` instead. */
-export type { ObjectQLKernelOptions, HookHandler, HookEntry, OperationContext, EngineMiddleware, ObjectQLHostContext } from '@objectstack/objectql';
+export type { HookHandler, HookEntry, OperationContext, EngineMiddleware, ObjectQLHostContext } from '@objectstack/objectql';
 
 // ── Plugin orchestration (downstream — stays in @objectql ecosystem) ──
 export * from './plugin';