feat(model): 双协议 LLM Provider（AnthropicChNativeAdapter /v1/messages + tool_use.input→Args 直接映射 + 流式重组）+ Provider 感知工厂/路由 + LLM_PROVIDER/anthropic 配置（OpenAI 兼容保留）

internal/config/config.go

@@ -54,12 +54,27 @@ type DBConfig struct {
 	PGURL      string `env:"DB_PG_URL"`
 }
 
-// LLMConfig holds the multi-supplier LLM adapter settings.
+// LLMConfig holds the multi-supplier LLM adapter settings. Provider selects the
+// wire protocol; every provider has its own independent base/key/model/fallback
+// so multiple vendors can coexist.
 type LLMConfig struct {
+	// Provider declares which protocol to use: "openai" (OpenAI-compatible
+	// /chat/completions) or "anthropic" (Anthropic Messages /v1/messages).
+	Provider string `env:"LLM_PROVIDER" default:"openai"`
+
+	// OpenAI-compatible provider (default). Kept flat for backward compatibility
+	// with the historic LLM_BASE_URL/API_KEY/MODEL/FALLBACK_MODEL env names.
 	BaseURL  string `env:"LLM_BASE_URL"`
 	APIKey   string `env:"LLM_API_KEY"`
 	Model    string `env:"LLM_MODEL"`
 	Fallback string `env:"LLM_FALLBACK_MODEL"`
+
+	// Anthropic native provider, used when Provider=anthropic. Independent
+	// config block so each vendor is a self-contained config.
+	AnthropicBaseURL  string `env:"ANTHROPIC_BASE_URL"`
+	AnthropicAPIKey   string `env:"ANTHROPIC_API_KEY"`
+	AnthropicModel    string `env:"ANTHROPIC_MODEL"`
+	AnthropicFallback string `env:"ANTHROPIC_FALLBACK_MODEL"`
 }
 
 // EmbeddingConfig holds the optional semantic embedding API settings. When