feat(dispatcher): Eino 采纳 Phase A —— llm.Pool 内部换成 Eino ChatModel 组件

把手写的 OpenAI HTTP/SSE 客户端换成 eino-ext/openai 的 ChatModel 组件：
- SetConfig 用激活配置构建 ChatModel（热更新=重建实例，读写锁保护）
- ChatStream → cm.Stream（StreamReader 逐 chunk）；Chat → cm.Generate
- 对外签名零变更（Chat/ChatStream/StreamText/Ready/ModelName），
  graph.go / report.go / memory_extract.go 不动
- Ready() 语义升级为「ChatModel 构建成功」，更准
- StreamText 降级桩保留

验收：make test-go 全模块绿；真实链路提交任务经新组件流式出答复
（28 字 + eval 1.00，Stream/Generate 两条路径都过）。

为 Phase B（BindTools 函数调用 + ADK）铺好底层组件。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

sundynix-dispatcher/go.mod

@@ -4,6 +4,7 @@ go 1.25.0
 
 require (
 	github.com/cloudwego/eino v0.9.9
+	github.com/cloudwego/eino-ext/components/model/openai v0.1.13
 	github.com/sundynix/sundynix-shared v0.0.0
 )
 
@@ -14,8 +15,11 @@ require (
 	github.com/bytedance/sonic v1.15.0 // indirect
 	github.com/bytedance/sonic/loader v0.5.0 // indirect
 	github.com/cloudwego/base64x v0.1.6 // indirect
+	github.com/cloudwego/eino-ext/libs/acl/openai v0.1.17 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/eino-contrib/jsonschema v1.0.3 // indirect
+	github.com/evanphx/json-patch v0.5.2 // indirect
+	github.com/google/uuid v1.6.0 // indirect
 	github.com/goph/emperror v0.17.2 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/compress v1.18.6 // indirect
@@ -23,6 +27,7 @@ require (
 	github.com/kr/pretty v0.3.1 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
+	github.com/meguminnnnnnnnn/go-openai v0.1.2 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/nats-io/nats.go v1.37.0 // indirect
@@ -34,7 +39,6 @@ require (
 	github.com/rogpeppe/go-internal v1.14.1 // indirect
 	github.com/sirupsen/logrus v1.9.4 // indirect
 	github.com/slongfield/pyfmt v0.0.0-20220222012616-ea85ff4c361f // indirect
-	github.com/stretchr/testify v1.11.1 // indirect
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/wk8/go-ordered-map/v2 v2.1.8 // indirect
 	github.com/yargevad/filepathx v1.0.0 // indirect