* feat(sandbox): add gpu sandbox scheduling support
Allow sandbox creation to request GPU resources explicitly or infer them from GPU image names. This wires GPU intent through bootstrap, validates gateway support, and adds dedicated GPU E2E coverage for follow-up cluster testing.
When --provider <name> is passed and no provider with that name exists on
the server, the CLI now checks if the name is a recognized provider type
(e.g. claude, nvidia, github). If it is, the provider is auto-created
from local credentials using the same discovery flow as inferred providers.
If the name is not a recognized type, the CLI returns a clear error
instead of deferring validation to the server.
This eliminates the FailedPrecondition error that occurred when passing
--provider nvidia on a fresh cluster where no providers had been created
yet.
Piotr Mlocek