Add Signal Channel

Adds Signal messaging support via a native adapter that speaks JSON-RPC to a signal-cli TCP daemon. No Chat SDK bridge — only Node.js builtins (node:net, node:child_process, node:fs).

Unlike Telegram or Discord, Signal has no bot API. NanoClaw registers as a full Signal account on a dedicated phone number (recommended) or links as a secondary device on your existing number.

Prerequisites

Java

signal-cli requires Java 17+:

java -version