refactor: hide llm adapter helpers

packages/llm/llm-deepseek/tests/serialize.spec.ts

@@ -1,7 +1,7 @@
 import { describe, expect, it } from 'vitest'
 import { CallId } from '@deepseek-ai/dsh-llm'
 import type { ContentBlock, GenerateOptions, Message } from '@deepseek-ai/dsh-llm'
-import { serializeMessages, serializeRequest } from '@deepseek-ai/dsh-llm-deepseek'
+import { serializeMessages, serializeRequest } from '../src/serialize.ts'
 
 function request(overrides: Partial<GenerateOptions> = {}): GenerateOptions {
   return { model: 'deepseek-v4-flash', messages: [], ...overrides }