David decided: Gated 'agents with own computer' workspace model to pro plan only

David directed the change using the production codebase and plan-gating infrastructure rather than adding new systems.

i want you to change the default model in the dropdown from 'auto' to gemini 3 flash. and also, i want you to make that 'agents — has its own computer' only a pro feature. ie. similar to the other models that are blocked for free/plus users, block that model too for free/plus users in the model dropdown. go onto the production db and codebase and study how plan limits and gating works so you dont break it or implement some new thing — just use the existing system

The constraint to reuse the existing gating system rather than inventing a new one is a recurring David pattern: extend existing infrastructure before adding new abstractions.