Add Matrix Channel

Adds Matrix support via the Chat SDK bridge.

Install

NanoClaw doesn't ship channels in trunk. This skill copies the Matrix adapter in from the channels branch.

Pre-flight (idempotent)

Skip to Credentials if all of these are already in place:

• src/channels/matrix.ts exists
• src/channels/index.ts contains import './matrix.js';
• @beeper/chat-adapter-matrix is listed in package.json dependencies

Otherwise continue. Every step below is safe to re-run.

1. Fetch the channels branch