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/wechat_kf/wechat_kf_cursor_store.py

@@ -0,0 +1,74 @@
+# -*- coding=utf-8 -*-
+"""
+Local-file based persistence for WeCom customer-service `next_cursor`.
+
+Why we need this:
+    The WeCom customer-service (微信客服) callback only notifies us that
+    "new messages exist". To actually fetch them we must call the
+    `cgi-bin/kf/sync_msg` endpoint with a `cursor` so that we only get
+    messages newer than the previously processed one. If we lose this
+    cursor (e.g. on process restart) WeCom will replay up to ~14 days of
+    history, which would cause the bot to flood users with duplicate
+    replies.
+
+This implementation deliberately avoids any external dependency
+(no Redis / no DB) — a single JSON file under the project's tmp dir is
+enough for a CoW-style single-process deployment.
+"""
+import json
+import os
+import threading
+from typing import Optional
+
+from common.log import logger
+
+
+class CursorStore:
+    """Thread-safe per-`open_kfid` cursor store backed by a JSON file."""
+
+    def __init__(self, file_path: str):
+        self._file_path = file_path
+        self._lock = threading.Lock()
+        self._data = self._load()
+
+    def _load(self) -> dict:
+        try:
+            if os.path.exists(self._file_path):
+                with open(self._file_path, "r", encoding="utf-8") as f:
+                    return json.load(f) or {}
+        except Exception as e:
+            logger.warning(f"[wechat_kf] failed to load cursor file {self._file_path}: {e}")
+        return {}
+
+    def _flush_locked(self):
+        # Atomic write: write to *.tmp first then rename, avoid corruption on crash.
+        tmp_path = self._file_path + ".tmp"
+        try:
+            os.makedirs(os.path.dirname(self._file_path) or ".", exist_ok=True)
+            with open(tmp_path, "w", encoding="utf-8") as f:
+                json.dump(self._data, f, ensure_ascii=False)
+            os.replace(tmp_path, self._file_path)
+        except Exception as e:
+            logger.warning(f"[wechat_kf] failed to flush cursor file {self._file_path}: {e}")
+            try:
+                if os.path.exists(tmp_path):
+                    os.remove(tmp_path)
+            except Exception:
+                pass
+
+    def get(self, open_kfid: str) -> Optional[str]:
+        with self._lock:
+            return self._data.get(open_kfid)
+
+    def set(self, open_kfid: str, cursor: str):
+        if not cursor:
+            return
+        with self._lock:
+            if self._data.get(open_kfid) == cursor:
+                return
+            self._data[open_kfid] = cursor
+            self._flush_locked()
+
+    def has(self, open_kfid: str) -> bool:
+        with self._lock:
+            return open_kfid in self._data