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/reasoning_shape_test.go

@@ -110,8 +110,8 @@ func TestOpenAIChat_DeclaredShapeSendsItsOwnSwitch(t *testing.T) {
 	}
 }
 
-// TestOpenAIChat_DeclaredShapeEnablesThinking pins the on direction as well, so the
-// switch cannot be hard-wired off by a refactor.
+// TestOpenAIChat_DeclaredShapeEnablesThinking 也钉住「开启」方向，
+// 以免开关被一次重构硬接成关闭。
 func TestOpenAIChat_DeclaredShapeEnablesThinking(t *testing.T) {
 	t.Parallel()
 	for _, tc := range declaredShapeCases {
@@ -226,9 +226,9 @@ func TestOpenAIChat_ReasoningKindOpenAIKeepsOpenAITiers(t *testing.T) {
 	}
 }
 
-// TestOpenAIChat_ReasoningKindOpenAIReportsBooleanSwitch asserts the effort-only
-// shape does not silently swallow a boolean thinking switch: it reports it, and
-// points at the documented way to disable reasoning.
+// TestOpenAIChat_ReasoningKindOpenAIReportsBooleanSwitch 断言「仅 effort」
+// 形状不会静默吞掉布尔 thinking 开关：它会报告该情况，并
+// 指出文档记录在案的关闭推理的做法。
 func TestOpenAIChat_ReasoningKindOpenAIReportsBooleanSwitch(t *testing.T) {
 	t.Parallel()
 	ch := make(chan capturedRequest, 1)
@@ -256,10 +256,10 @@ func TestOpenAIChat_ReasoningKindOpenAIReportsBooleanSwitch(t *testing.T) {
 	}
 }
 
-// TestOpenAIChat_UnknownReasoningKindSendsNothing asserts a shape this build does
-// not implement is reported and sends nothing — even when the model name would
-// otherwise look like a vendor we do understand. Guessing here is exactly the
-// "fake adaptation" the ruling forbids.
+// TestOpenAIChat_UnknownReasoningKindSendsNothing 断言本次构建
+// 未实现的形状会被上报、且什么都不发——即便模型名
+// 看上去像我们确实理解的厂商也一样。在这里靠猜正是
+// 裁决所禁止的「假适配」。
 func TestOpenAIChat_UnknownReasoningKindSendsNothing(t *testing.T) {
 	t.Parallel()
 	ch := make(chan capturedRequest, 1)
@@ -288,9 +288,9 @@ func TestOpenAIChat_UnknownReasoningKindSendsNothing(t *testing.T) {
 	}
 }
 
-// TestOpenAIChat_AutoQwenShapeStaysConservative pins the un-declared default: a
-// Qwen endpoint may be vLLM or DashScope, whose field shapes differ, so auto mode
-// sends nothing and asks for an explicit declaration instead of guessing one.
+// TestOpenAIChat_AutoQwenShapeStaysConservative 钉住未声明的默认：
+// Qwen 端点可能是 vLLM 或 DashScope，两者字段形状不同，所以 auto 模式
+// 什么都不发，并改为要求显式声明，而不是替它猜一个。
 func TestOpenAIChat_AutoQwenShapeStaysConservative(t *testing.T) {
 	t.Parallel()
 	ch := make(chan capturedRequest, 1)