fix: salvage follow-ups for Weixin adapter (#6747)

- Remove sys.path.insert hack (leftover from standalone dev)
- Add token lock (acquire_scoped_lock/release_scoped_lock) in
  connect()/disconnect() to prevent duplicate pollers across profiles
- Fix get_connected_platforms: WEIXIN check must precede generic
  token/api_key check (requires both token AND account_id)
- Add WEIXIN_HOME_CHANNEL_NAME to _EXTRA_ENV_KEYS
- Add gateway setup wizard with QR login flow
- Add platform status check for partially configured state
- Add weixin.md docs page with full adapter documentation
- Update environment-variables.md reference with all 11 env vars
- Update sidebars.ts to include weixin docs page
- Wire all gateway integration points onto current main

Salvaged from PR #6747 by Zihan Huang.

hermes_cli/tools_config.py

@@ -133,6 +133,7 @@ PLATFORMS = {
  "dingtalk": {"label": "💬 DingTalk", "default_toolset": "hermes-dingtalk"},
     "feishu": {"label": "🪽 Feishu", "default_toolset": "hermes-feishu"},
     "wecom": {"label": "💬 WeCom", "default_toolset": "hermes-wecom"},
+    "weixin": {"label": "💬 Weixin", "default_toolset": "hermes-weixin"},
     "api_server": {"label": "🌐 API Server", "default_toolset": "hermes-api-server"},
     "mattermost": {"label": "💬 Mattermost", "default_toolset": "hermes-mattermost"},
     "webhook": {"label": "🔗 Webhook", "default_toolset": "hermes-webhook"},