Requested Solution

Add support for routing runs to different worker pools based on run type. The most common use case is:

• PROPOSED (PR previews) → public worker pool

• TRACKED (main branch deploys) → private worker pool

This could be implemented as a new policy type (e.g. WORKER_POOL) or as a per-stack configuration with two fields: worker_pool_proposed and worker_pool_tracked.

Use Case

Organizations on plans with a limited number of private workers want to use them efficiently. Private workers are ideal for tracked runs — they cache Docker layers and run on faster hardware. PR previews (proposed runs), however, are frequent and short-lived, making the public fleet a better fit for them.

Today, worker pool assignment is stack-level only. Setting a private pool on a stack routes all runs — both proposed and tracked — to that pool, consuming the private worker even for PR previews. This forces a choice: either waste private worker capacity on previews, or don't use the private pool at all.