fix(ai): use concrete middleware module paths in the rerank activity

rerank/index.ts imported the '../middleware' directory barrel, so the
declaration emit rewrote it to '../middleware.js', which does not
resolve under bundler/node16/nodenext. scan-dangling-dts caught it.

Import '../middleware/run' and '../middleware/types' like every other
activity does.

Author: AlemTuzlak

packages/ai/src/activities/rerank/index.ts

@@ -15,10 +15,10 @@ import {
   runGenerationFinish,
   runGenerationStart,
   runGenerationUsage,
-} from '../middleware'
+} from '../middleware/run'
 import type { InternalLogger } from '../../logger/internal-logger'
 import type { DebugOption } from '../../logger/types'
-import type { GenerationMiddleware } from '../middleware'
+import type { GenerationMiddleware } from '../middleware/types'
 import type { RerankAdapter } from './adapter'
 import type { RerankResult } from '../../types'