docs(comments): 注释中文化 · internal/runtime/multimodal（21 文件，纯替换）

- 只翻注释/文档字符串，代码零变化：go/scanner 词法流比对 21 文件 token+字面量全等，增删行数 1:1（467/467）
- 刻意保留非散文英文：JSON Schema description、工具 Description() 返回值、adapter prompt、API 路径与命令示例、环境变量名
- 逐行确认代码前缀未变，未触碰其他模块

internal/runtime/multimodal/voice/errors.go

@@ -2,17 +2,17 @@ package voice
 
 import "errors"
 
-// Sentinel errors returned by the voice package. Each is wrapped with %w so
-// callers can test for a category while keeping the cause.
+// voice 包返回的哨兵错误。每个错误都以 %w 包装，
+// 使调用方能按类别判断，同时保留原始原因。
 var (
-	// ErrProviderFailed is returned when every provider in a chain fails.
+	// ErrProviderFailed 在一条链上所有提供方都失败时返回。
 	ErrProviderFailed = errors.New("voice: all providers failed")
-	// ErrNotConfigured is returned when a provider has no endpoint/setting.
+	// ErrNotConfigured 在提供方缺少 endpoint/配置项时返回。
 	ErrNotConfigured = errors.New("voice: provider not configured")
-	// ErrNotImplemented is returned by an adaptation-point provider.
+	// ErrNotImplemented 由适配点提供方返回。
 	ErrNotImplemented = errors.New("voice: provider not implemented")
-	// ErrEmptyText is returned when TTS receives empty text.
+	// ErrEmptyText 在 TTS 收到空文本时返回。
 	ErrEmptyText = errors.New("voice: empty text")
-	// ErrClosed is returned when a service call arrives after Close.
+	// ErrClosed 在 Close 之后仍有服务调用到达时返回。
 	ErrClosed = errors.New("voice: service closed")
 )