Remove the Echo agent

docs/user/develop/practice/llm-adapter.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write
-llm-adapter.md: 83296e54220c668410fe69d689199171251a7787
-llm-adapter.zh.md: 89b7185690dbdfe33cbafe7b0ee4c3e83cfe0df8
+llm-adapter.md: 3e83289b8072ef231f83c0fa3cfe3260547b42fa
+llm-adapter.zh.md: 92fcf9b22f4bb356ada4c46f9a03ef0cc2d159da

docs/user/develop/practice/llm-adapter.md

@@ -145,9 +145,8 @@ The repository contains complete implementations:
 
 - `packages/llm/llm-deepseek/` — DeepSeek API adapter using the OpenAI-compatible format
 - `packages/llm/llm-pi-ai/` — Pi AI adapter using a different API format
-- `examples/echo-agent/src/mock-llm.ts` — minimal local teaching adapter
 
-Start with the mock adapter to study a complete chunk sequence without network behavior.
+Compare the two shipped adapters to see the same harness contract implemented over different provider SDKs.
 
 ## Error handling
 

docs/user/develop/practice/llm-adapter.zh.md

@@ -145,9 +145,8 @@ ctx.llm.registerAdapter(['model-name-1', 'model-name-2'], adapter)
 
 - `packages/llm/llm-deepseek/` — DeepSeek API 适配器（OpenAI 兼容格式）
 - `packages/llm/llm-pi-ai/` — Pi AI 适配器（不同的 API 格式）
-- `examples/echo-agent/src/mock-llm.ts` — 最简 mock 适配器（教学用）
 
-mock 适配器是学习 StreamChunk 协议的最佳起点——它用纯本地逻辑演示了完整的 chunk 序列。
+对比这两个已交付的适配器，可以看到同一套 harness 契约如何在不同提供方 SDK 之上实现。
 
 ## 错误处理