feat(channels): add mock channel package for E2E testing

- Add @qwen-code/channel-mock package with MockPluginChannel
- Add createMockServer for programmatic test control via WebSocket
- Refactor integration test to use real WebSocket E2E flow

This enables testing the full channel pipeline (WebSocket → ChannelBase → AcpBridge → agent)
instead of the previous in-process loopback approach.

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

package-lock.json

@@ -12,7 +12,8 @@
         "packages/channels/base",
         "packages/channels/telegram",
         "packages/channels/weixin",
-        "packages/channels/dingtalk"
+        "packages/channels/dingtalk",
+        "packages/channels/mock"
       ],
       "dependencies": {
         "@testing-library/dom": "^10.4.1",
@@ -3002,6 +3003,10 @@
       "resolved": "packages/channels/dingtalk",
       "link": true
     },
+    "node_modules/@qwen-code/channel-mock": {
+      "resolved": "packages/channels/mock",
+      "link": true
+    },
     "node_modules/@qwen-code/channel-telegram": {
       "resolved": "packages/channels/telegram",
       "link": true
@@ -18985,6 +18990,17 @@
         "typescript": "^5.0.0"
       }
     },
+    "packages/channels/mock": {
+      "name": "@qwen-code/channel-mock",
+      "version": "0.1.0",
+      "dependencies": {
+        "@qwen-code/channel-base": "file:../base",
+        "ws": "^8.18.0"
+      },
+      "devDependencies": {
+        "@types/ws": "^8.5.0"
+      }
+    },
     "packages/channels/telegram": {
       "name": "@qwen-code/channel-telegram",
       "version": "0.1.0",