add-webex

为 NanoClaw 添加 Cisco Webex 通道，允许代理在 Webex 中通信。

把 Cisco Webex 通道接入现有代理系统，让代理能在 Webex 里收发消息和互动。用在需要把机器人/代理铺到企业协作平台、对接企业会议和消息流时。实现上通过 Chat SDK 桥接、复制已有 adapter，并用可重复执行的指令步骤来保证变更可重放和可回滚。

# Add Webex Channel

Adds Cisco Webex support via the Chat SDK bridge. NanoClaw doesn't ship channels
in trunk — this skill copies the Webex adapter in from the `channels` branch.

The mechanical steps under **Apply** carry `nc:` directive fences: an agent
reads the prose and applies them, and a parser can apply them deterministically
from the same document. Every directive is idempotent, so the whole skill is
safe to re-run; anything a parser can't apply falls back to the prose beside it.

## Apply

### 1. Copy the adapter and its registration test

Fetch the `channels` branch and copy the Webex adapter and its registration test
into `src/channels/` (overwrite — the branch is canonical):

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