Split large controller test files for maintainability

[Defilan]

Context

Several test files have grown large enough to impact navigability for new contributors:

File	Lines	Concern
internal/controller/inferenceservice_controller_test.go	2,587	Primary candidate
pkg/cli/benchmark_test.go	1,786	Large but focused
pkg/cli/cache_inspect_test.go	1,131	Large but focused
internal/controller/model_controller_test.go	912	Borderline

Proposed Approach

For inferenceservice_controller_test.go, split by functionality:

• inferenceservice_reconcile_test.go — core reconciliation tests
• inferenceservice_deployment_test.go — deployment construction tests
• inferenceservice_storage_test.go — storage config tests (cached, emptyDir, PVC)
• inferenceservice_service_test.go — service construction tests
• inferenceservice_scheduling_test.go — GPU queue / priority tests

All files stay in the controller package and use the same suite_test.go setup.

Priority

Low — code works fine, this is purely for contributor experience.