docs(comments): 注释中文化 · internal/runtime/model + internal/services/backthink（54 文件，纯替换）

- 只翻注释/文档字符串：`go/scanner` 剥注释后按 token 序列+literal 逐 token 比对，**54/54 文件 SAME**；
  改动文件总行数与 HEAD 漂移 = 0（严格 1:1，无合并/拆行）
- 裁决编号与 design 节号逐字保留（03.4.1/03.4.2/03.4.3/14.4.1/14.4.5/07.4.2-4、design/04 §3.1/§3.2 等）；
  `chat_template_kwargs` / `enable_thinking` / `reasoning_effort` / `thinking:{type}` 字段名与形状说明未动
- 存疑译法（已登记）：`persona` 在叙事语境用「角色」、标识符语境保留 `persona`（仓库既有模块本身混用）；
  `rung`→「级」；`provider` 存在「提供商/提供者」两种落笔（可按需一键统一）
- 复核：build/vet 绿 + 两包测试绿；gofmt 干净；残留英文注释 0 条
- 既有存量（未修，只报告）：`model/anthropic_test.go` 612 行 >500；`applyAnthropicEvent` 115 行 >80

internal/runtime/model/local_rung_test.go

@@ -13,10 +13,10 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
 )
 
-// recordingServer is an OpenAI-compatible /chat/completions endpoint that records
-// the model name of every request and either fails or succeeds. It backs the
-// local-rung tests (裁决 03.4.3): the point of the rung is that a request reaches
-// the local endpoint with the local model name, and never when the rung is off.
+// recordingServer 是一个 OpenAI 兼容的 /chat/completions 端点，记录
+// 每个请求的模型名，并或失败或成功。它支撑
+// 本地级测试（裁决 03.4.3）：该级的意义在于请求以本地模型名
+// 到达本地端点，而该级关闭时绝不如此。
 type recordingServer struct {
 	mu     sync.Mutex
 	models []string
@@ -51,9 +51,9 @@ func newRecordingServer(t *testing.T, fail bool) (*httptest.Server, *recordingSe
 	return srv, rec
 }
 
-// TestNewChatChainWithLog_LocalRungAppended verifies the third degradation level
-// (primary → fallback → local) only joins the chain when it is enabled AND fully
-// configured.
+// TestNewChatChainWithLog_LocalRungAppended 验证第三级降级
+// （primary → fallback → local）只在启用且完全
+// 配置好时才加入链。
 func TestNewChatChainWithLog_LocalRungAppended(t *testing.T) {
 	t.Parallel()
 	cases := []struct {
@@ -88,9 +88,9 @@ func TestNewChatChainWithLog_LocalRungAppended(t *testing.T) {
 	}
 }
 
-// TestChain_Chat_LocalRungServesAfterFallback verifies the local rung really takes
-// over the request after the primary and fallback steps fail, with the local model
-// name on the wire and the local endpoint's own base URL/API key (not the group's).
+// TestChain_Chat_LocalRungServesAfterFallback 验证本地级在主
+// 步骤与降级步骤都失败后真的接管请求，且线上用
+// 本地模型名与本地端点自己的 base URL/API key（而非组的）。
 func TestChain_Chat_LocalRungServesAfterFallback(t *testing.T) {
 	t.Parallel()
 	mainSrv, _ := newRecordingServer(t, true)
@@ -117,9 +117,9 @@ func TestChain_Chat_LocalRungServesAfterFallback(t *testing.T) {
 	}
 }
 
-// TestChain_Chat_LocalRungOffNeverCalled pins the default-off red line: with the
-// rung disabled the local endpoint must never be touched, even when every other
-// step fails.
+// TestChain_Chat_LocalRungOffNeverCalled 钉住默认关闭的红线：该级
+// 禁用时绝不能触碰本地端点，即便其它所有
+// 步骤都失败。
 func TestChain_Chat_LocalRungOffNeverCalled(t *testing.T) {
 	t.Parallel()
 	mainSrv, _ := newRecordingServer(t, true)
@@ -141,14 +141,14 @@ func TestChain_Chat_LocalRungOffNeverCalled(t *testing.T) {
 	}
 }
 
-// TestChain_Chat_PrimaryStepKeepsRoutedModel pins that the chain does not discard
-// the router's decision: the primary step sends the request's routed model, and
-// the fallback step still pins its own configured model (裁决 03.4.1).
+// TestChain_Chat_PrimaryStepKeepsRoutedModel 钉住链不会丢弃
+// 路由器的决策：主步骤发送请求中被路由的模型，而
+// 降级步骤仍钉住自己配置的模型（裁决 03.4.1）。
 func TestChain_Chat_PrimaryStepKeepsRoutedModel(t *testing.T) {
 	t.Parallel()
-	// One endpoint serves both steps (the factory builds every step against the
-	// group's base URL): it fails for anything but the fallback model, so the
-	// recorded model names show which model each step actually sent.
+	// 一个端点同时服务两个步骤（工厂让每一步都针对
+	// 组的 base URL 构建）：除降级模型外它都失败，所以
+	// 记录下来的模型名显示了每一步实际发送了哪个模型。
 	rec := &recordingServer{}
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		var body struct {