refactor(core,server): 简化配置加载，移除 workdir 参数

Provider 和 Agent 配置统一从全局目录加载，无需传递 workdir：
- ProviderRegistry.init() 不再需要 workdir 参数
- AgentRegistry.init() 不再需要 workdir 参数
- 配置文件路径统一使用 ~/.ai-terminal-assistant/

packages/server/src/routes/agents.ts

@@ -74,7 +74,7 @@ interface AgentConfigFile {
 // Core Agent 模块类型
 interface AgentModule {
   agentRegistry: {
-    init: (workdir: string) => Promise<void>;
+    init: () => Promise<void>;
     get: (name: string) => AgentInfo | undefined;
     list: () => AgentInfo[];
   };
@@ -152,8 +152,7 @@ async function ensureRegistryInitialized(): Promise<boolean> {
   if (!module) return false;
 
   if (!initialized) {
-    const config = getConfig();
-    await module.agentRegistry.init(config.workdir);
+    await module.agentRegistry.init();
     initialized = true;
   }
 

packages/server/src/routes/providers.ts

@@ -247,7 +247,7 @@ providersRouter.post('/', async (c) => {
 
     const registry = core.getProviderRegistry();
     registry.registerCustom(body);
-    await registry.saveConfig(getConfig().workdir);
+    await registry.saveConfig();
 
     return c.json({
       success: true,
@@ -285,7 +285,7 @@ providersRouter.put('/:id', async (c) => {
     }
 
     registry.setConfig(id, { ...body, id });
-    await registry.saveConfig(getConfig().workdir);
+    await registry.saveConfig();
 
     return c.json({
       success: true,
@@ -321,7 +321,7 @@ providersRouter.delete('/:id', async (c) => {
       return c.json({ success: false, error: `Provider not found: ${id}` }, 404);
     }
 
-    await registry.saveConfig(getConfig().workdir);
+    await registry.saveConfig();
 
     return c.json({
       success: true,
@@ -365,7 +365,7 @@ providersRouter.post('/:id/models', async (c) => {
 
     const registry = core.getProviderRegistry();
     registry.addCustomModel(providerId, body);
-    await registry.saveConfig(getConfig().workdir);
+    await registry.saveConfig();
 
     return c.json({
       success: true,
@@ -408,7 +408,7 @@ providersRouter.delete('/:id/models/:modelId', async (c) => {
       );
     }
 
-    await registry.saveConfig(getConfig().workdir);
+    await registry.saveConfig();
 
     return c.json({
       success: true,