refactor: 创建 @anthropic-ai/model-provider 包骨架与类型定义

- 新建 workspace 包 packages/@anthropic-ai/model-provider
- 定义 ModelProviderHooks 接口（依赖注入：分析、成本、日志等）
- 定义 ClientFactories 接口（Anthropic/OpenAI/Gemini/Grok 客户端工厂）
- 搬入核心类型：Message 体系、NonNullableUsage、EMPTY_USAGE、SystemPrompt、错误常量
- 主项目 src/types/message.ts 等改为 re-export，保持向后兼容

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/@anthropic-ai/model-provider/src/index.ts

@@ -0,0 +1,63 @@
+// @anthropic-ai/model-provider
+// Model provider abstraction layer for Claude Code
+//
+// This package owns the model calling logic and provides:
+// - Core query functions (queryModelWithStreaming, etc.)
+// - Provider implementations (Anthropic, OpenAI, Gemini, Grok)
+// - Type definitions (Message, Tool, Usage, etc.)
+// - Dependency injection hooks (analytics, cost tracking, etc.)
+//
+// Initialization:
+//   registerClientFactories({ ... })  // inject auth clients
+//   registerHooks({ ... })            // inject analytics/cost/logging
+
+// Hooks (dependency injection)
+export { registerHooks, getHooks } from './hooks/index.js'
+export type { ModelProviderHooks } from './hooks/types.js'
+
+// Client factories
+export { registerClientFactories, getClientFactories } from './client/index.js'
+export type { ClientFactories } from './client/types.js'
+
+// Types
+export * from './types/index.js'
+
+// Provider model mappings
+export { resolveOpenAIModel } from './providers/openai/modelMapping.js'
+export { resolveGrokModel } from './providers/grok/modelMapping.js'
+export { resolveGeminiModel } from './providers/gemini/modelMapping.js'
+
+// Gemini provider utilities
+export { anthropicMessagesToGemini } from './providers/gemini/convertMessages.js'
+export { anthropicToolsToGemini, anthropicToolChoiceToGemini } from './providers/gemini/convertTools.js'
+export { adaptGeminiStreamToAnthropic } from './providers/gemini/streamAdapter.js'
+export {
+  GEMINI_THOUGHT_SIGNATURE_FIELD,
+  type GeminiContent,
+  type GeminiGenerateContentRequest,
+  type GeminiPart,
+  type GeminiStreamChunk,
+  type GeminiTool,
+  type GeminiFunctionCallingConfig,
+  type GeminiFunctionDeclaration,
+  type GeminiFunctionCall,
+  type GeminiFunctionResponse,
+  type GeminiInlineData,
+  type GeminiUsageMetadata,
+  type GeminiCandidate,
+} from './providers/gemini/types.js'
+
+// Error utilities
+export {
+  formatAPIError,
+  extractConnectionErrorDetails,
+  sanitizeAPIError,
+  getSSLErrorHint,
+  type ConnectionErrorDetails,
+} from './errorUtils.js'
+
+// Shared OpenAI conversion utilities
+export { anthropicMessagesToOpenAI } from './shared/openaiConvertMessages.js'
+export type { ConvertMessagesOptions } from './shared/openaiConvertMessages.js'
+export { anthropicToolsToOpenAI, anthropicToolChoiceToOpenAI } from './shared/openaiConvertTools.js'
+export { adaptOpenAIStreamToAnthropic } from './shared/openaiStreamAdapter.js'