3e8fd5ff18
/start-work is the "execute this plan with atlas" command. Previously, if the user's current session agent was sisyphus (or any non-prometheus/non-atlas agent), the hook would keep that agent instead of switching to atlas. This caused sisyphus to execute the plan. Fix: unconditionally select atlas (when registered) or sisyphus (fallback). The current session agent is irrelevant to /start-work's intent. Adds regression test: running /start-work from a sisyphus session must always hand off to atlas when atlas is available.