feat(channels): add crash recovery and gateway mode support

- Add session persistence to SessionRouter for crash recovery
- Add loadSession method to AcpBridge for restoring sessions
- Add ChannelBaseOptions to support external router injection
- Refactor start.ts to support both standalone and gateway modes
- Extract config utilities into separate module

This enables channels to recover sessions after bridge crashes and
supports running multiple channels under a gateway process.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/channels/base/src/AcpBridge.ts

@@ -129,6 +129,16 @@ export class AcpBridge extends EventEmitter {
     return response.sessionId;
   }
 
+  async loadSession(sessionId: string, cwd: string): Promise<string> {
+    const conn = this.ensureConnection();
+    const response = await conn.loadSession({
+      sessionId,
+      cwd,
+      mcpServers: [],
+    });
+    return response.sessionId;
+  }
+
   async prompt(
     sessionId: string,
     text: string,