fix(llm): 工具路由配置修改后立即生效，不再硬编码 system prompt

toolrouter 每轮调用都从 DB 读取最新配置，/admin/llm/api 保存后下一条消息即生效，
无需重启。ai.NewService 启动时从 DB 加载初始配置，移除硬编码 prompt 覆盖用户配置的问题。

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

internal/toolrouter/loop.go

@@ -60,8 +60,8 @@ func RunAgentToolLoop(ctx context.Context, state *State, profile *llm.Profile, s
 	if emit != nil {
 		emit(stream.Frame{Type: "trace", Tool: "agent_tools", Stage: "prepare", Status: "success", Message: "已准备可用工具", Data: map[string]any{"tools": availableNames, "tool_descriptions": toolDescriptions}})
 	}
-	if state == nil || state.cfg == nil {
-		// No tool router config, but we have tools - use primary system prompt
+	if state == nil {
+		// No tool router state, but we have tools - use primary system prompt
 		if strings.TrimSpace(systemPrompt) != "" {
 			systemMessage := &model.ChatCompletionMessage{
 				Role: "system",
@@ -74,8 +74,10 @@ func RunAgentToolLoop(ctx context.Context, state *State, profile *llm.Profile, s
 		}
 		return finalMessages, nil
 	}
+	// 每轮调用都重新加载最新配置，确保管理员在 /admin/llm/api 保存后立即生效
+	cfg := state.effectiveConfig()
 	// Use tool router system prompt if available, otherwise fall back to primary system prompt
-	prompt := strings.TrimSpace(state.cfg.SystemPrompt)
+	prompt := strings.TrimSpace(cfg.SystemPrompt)
 	if prompt == "" {
 		prompt = strings.TrimSpace(systemPrompt)
 	}
@@ -96,11 +98,11 @@ func RunAgentToolLoop(ctx context.Context, state *State, profile *llm.Profile, s
 		resp, err := completion.CompleteChat(ctx, routerProfile, model.CreateChatCompletionRequest{
 			Model:             routerProfile.Config.Model,
 			Messages:          decisionMessages,
-			MaxTokens:         &state.cfg.MaxTokens,
+			MaxTokens:         &cfg.MaxTokens,
 			Tools:             definitions,
 			ToolChoice:        model.ToolChoiceStringTypeAuto,
 			ParallelToolCalls: BoolPtr(false),
-		}, time.Duration(state.cfg.Timeout)*time.Second)
+		}, time.Duration(cfg.Timeout)*time.Second)
 		if err != nil {
 			return finalMessages, err
 		}

internal/toolrouter/state.go

@@ -17,15 +17,30 @@ type Config struct {
 	SystemPrompt string
 }
 
+// ConfigStore 定义从持久化层读取最新 ToolRouter 配置的能力。
+// 每次 RunAgentToolLoop 都会调用 LoadToolRouterConfig，从而保证管理员
+// 在 /admin/llm/api 修改配置后立即生效，无需重启。
+type ConfigStore interface {
+	LoadToolRouterConfig() (*Config, error)
+}
+
 // State manages the tool router state
 type State struct {
-	cfg *Config
-	ai  *llm.State
+	cfg   *Config
+	ai    *llm.State
+	store ConfigStore
 }
 
 // Option is a function that configures the State
 type Option func(*State)
 
+// WithConfigStore 注入运行时配置加载器，State 会在每次需要时拉取最新配置。
+func WithConfigStore(store ConfigStore) Option {
+	return func(s *State) {
+		s.store = store
+	}
+}
+
 // NewState creates a new tool router state
 func NewState(cfg *Config, ai *llm.State, options ...Option) (*State, error) {
 	if cfg == nil {
@@ -51,12 +66,31 @@ func NewState(cfg *Config, ai *llm.State, options ...Option) (*State, error) {
 	return state, nil
 }
 
+// effectiveConfig 返回当前生效的配置：优先从 store 加载最新值，加载失败时回退到内存 cfg。
+// 调用方拿到的永远是非 nil 指针；内存 cfg 也保持同步以便其它读取点。
+func (s *State) effectiveConfig() *Config {
+	if s == nil {
+		return &Config{}
+	}
+	if s.store != nil {
+		if latest, err := s.store.LoadToolRouterConfig(); err == nil && latest != nil {
+			s.cfg = latest
+			return latest
+		}
+	}
+	if s.cfg == nil {
+		return &Config{}
+	}
+	return s.cfg
+}
+
 // RouterProfile returns the LLM profile configured for the tool router
 func (s *State) RouterProfile(fallback *llm.Profile) *llm.Profile {
-	if s == nil || s.cfg == nil || s.ai == nil {
+	if s == nil || s.ai == nil {
 		return fallback
 	}
-	name := strings.TrimSpace(s.cfg.OpenAIName)
+	cfg := s.effectiveConfig()
+	name := strings.TrimSpace(cfg.OpenAIName)
 	if name == "" {
 		return fallback
 	}
@@ -69,8 +103,8 @@ func (s *State) RouterProfile(fallback *llm.Profile) *llm.Profile {
 
 // Config returns a copy of the current configuration
 func (s *State) Config() Config {
-	if s == nil || s.cfg == nil {
+	if s == nil {
 		return Config{}
 	}
-	return *s.cfg
+	return *s.effectiveConfig()
 }