[EPIC] Workspace Filter Rules

### Certification

- [x] I certify I am an Epic Owner for Kubeflow Notebooks 2.0 and expected to create planning-related issues.

### User Story

As an AI/ML practitioner, Bella needs to easily and confidently select the correct configurations for her Workspace. When setting up a new workspace, she wants the platform to intelligently guide her by automatically filtering out incompatible WorkspaceKind, podConfig and/or imageConfig options based on her choices or the specific namespace she's working in. For instance, if she selects an image requiring GPU support, she expects to only see podConfig options that provide GPUs, preventing her from accidentally launching an unusable environment.

This streamlined selection process allows Bella to quickly and accurately provision her workspace without needing to manually verify every compatibility detail, ensuring her environments are correctly configured from the start and accelerating her development workflow.

No files, tests, or entry points are identified. Start by breaking the user story into WorkspaceKind, podConfig, imageConfig, and namespace compatibility rules, then locate the existing workspace configuration and selection paths. Done means incompatible options are filtered before provisioning and the supported combinations are covered by tests.

Written by the indexing model from the issue text.