refactor(wechat_kf): rename channel from wechatcom_kf and split corp_id

Rename the WeCom customer-service channel and give it its own corp_id
field so users no longer have to share `wechatcom_corp_id` with the
self-built WeCom app channel.

Renames (channel-side):
- channel type / const: wechatcom_kf -> wechat_kf
- package dir: channel/wechatcom_kf/ -> channel/wechat_kf/
- python files / classes: WechatComKf* -> WechatKf*
- config keys: wechatcom_kf_{secret,token,aes_key,port} ->
  wechat_kf_{secret,token,aes_key,port}; new wechat_kf_corp_id
- env vars: WECHATCOM_KF_* -> WECHAT_KF_*; new WECHAT_KF_CORP_ID
- log prefix / cursor file: [wechatcom_kf] -> [wechat_kf]
- web console CHANNEL_DEFS key + startup log line

Renames (docs):
- docs/channels/wecom-kf.mdx -> docs/channels/wechat-kf.mdx (zh/en/ja)
- update docs.json sidebar entries and all field names inside the docs

In addition, the Web Console "微信客服" entry now exposes its own
Corp ID field instead of reusing the wechatcom_app one, and includes
the screenshot of the visual config in the channel guide.

Web Console onboarding section is added (Tabs: Web Console / config
file) and the local URL `http://127.0.0.1:9899/` parenthetical is
dropped for consistency with other channel docs.

Co-authored-by: Cursor <cursoragent@cursor.com>

channel/channel_factory.py

@@ -27,9 +27,9 @@ def create_channel(channel_type) -> Channel:
     elif channel_type == "wechatcom_app":
         from channel.wechatcom.wechatcomapp_channel import WechatComAppChannel
         ch = WechatComAppChannel()
-    elif channel_type == const.WECHATCOM_KF:
-        from channel.wechatcom_kf.wechatcom_kf_channel import WechatComKfChannel
-        ch = WechatComKfChannel()
+    elif channel_type == const.WECHAT_KF:
+        from channel.wechat_kf.wechat_kf_channel import WechatKfChannel
+        ch = WechatKfChannel()
     elif channel_type == const.FEISHU:
         from channel.feishu.feishu_channel import FeiShuChanel
         ch = FeiShuChanel()