[Bug] Watch round notifications spam Teams channel — need notify level + attribution #804

Problem

squad watch prints 🔄 Ralph — Round N on every round, even when the board is empty. When forwarded to a Teams channel via webhook/bridge, this produces hundreds of noisy messages like:

• Squad Monitor Round 160
• Squad Monitor Round 161

Users can't tell which machine or repo these come from.

Fix

• --notify-level important (default): only print rounds with actual work
• --notify-level all: old behavior
• --notify-level none: suppress all
• Machine name (os.hostname()) and repo name in round headers
• Configurable in .squad/config.json: { ""watch"": { ""notifyLevel"": ""important"" } }