Why were they deprecated?
Workflows are not decprecated -- we paused making improvements to it to focus on squads.
How long will they be supported?
Workflows will not be going away. It was always be available on the dashboard.
Can Squads offer the same fine grained control (conditional outbound edges from Agent Nodes)?
Yes they can, Checkout Handoff tool --
https://docs.vapi.ai/tools/handoff