feat(core): 增强 Plan Agent 支持细粒度 bash 权限和模式切换

- Plan Agent 细粒度 bash 权限：允许只读命令 (ls, grep, git log 等)，
  禁止危险操作 (rm, mv, git commit 等)
- 新增 plan_mode_respond 工具：结构化输出计划、进度和探索状态
- Agent.switchMode() 方法：支持 Build ↔ Plan 模式切换保留对话历史
- WebSocket mode_switch 消息：支持运行时动态切换模式
- 更新 Plan Agent prompt 引导使用 plan_mode_respond 工具

packages/server/src/ws.ts

@@ -6,7 +6,7 @@
 
 import type { WSContext } from 'hono/ws';
 import { getSessionManager } from './session/manager.js';
-import { processMessage, cancelProcessing } from './agent/index.js';
+import { processMessage, cancelProcessing, getOrCreateAgent } from './agent/index.js';
 import { handlePermissionResponse, setSessionAutoApprove } from './permission/handler.js';
 import type { ClientMessage, ServerMessage } from './types.js';
 
@@ -172,6 +172,35 @@ export async function handleWebSocketMessage(
         break;
       }
 
+      case 'mode_switch': {
+        // 动态模式切换（Build ↔ Plan）
+        const mode = message.payload?.agentMode as 'build' | 'plan' | undefined;
+        if (mode === 'build' || mode === 'plan') {
+          try {
+            const agent = await getOrCreateAgent(sessionId);
+            if (agent && typeof agent.switchMode === 'function') {
+              agent.switchMode(mode, true); // 保留对话历史
+              broadcastToSession(sessionId, {
+                type: 'mode_switched',
+                sessionId,
+                payload: { mode },
+              });
+              console.log(`[WS] Mode switched for session ${sessionId}: ${mode}`);
+            } else {
+              console.warn(`[WS] Agent does not support switchMode for session ${sessionId}`);
+            }
+          } catch (error) {
+            console.error(`[WS] Failed to switch mode for session ${sessionId}:`, error);
+            broadcastToSession(sessionId, {
+              type: 'error',
+              sessionId,
+              payload: { message: 'Failed to switch mode' },
+            });
+          }
+        }
+        break;
+      }
+
       default:
         ws.send(
           JSON.stringify({