Add config option to disable progress streaming to chat channels

[tobyshi]

Problem

When using nanobot via Telegram (or other chat channels), intermediate tool execution steps are streamed as separate messages:
exec("grep ...")
read_file(...)
exec("todoist add ...")

This creates 10-15+ messages on some interactions, cluttering the chat.

Root Cause

In nanobot/agent/loop.py, the _bus_progress() function publishes every progress update as an OutboundMessage to the bus, which chat channels receive as real messages.

Proposed Solution

Add a config option to disable progress streaming:

json
{
"show_progress": false
}

Tank you!