After wiring a channel to an agent group, register.ts writes a task
message to the session that triggers the /welcome container skill.
The agent introduces itself immediately — the user sees typing and
then a greeting without having to send a message first.
Uses kind 'task' (not 'system') so the poll loop picks it up normally.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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