Docs update needed: Deleting radius-system namespace may hang

What content needs to be created or modified?

The documentation should be updated to include troubleshooting steps and expected behavior when deleting the radius-system namespace. According to this issue in the radius repo, users may experience indefinite hangs due to resource deletion failures and remaining pods. Documentation should address:

• What happens during deletion
• Why the namespace may hang (e.g., remaining pods, API discovery failures)
• How to resolve or troubleshoot the problem

Describe the solution you'd like

A new troubleshooting section should be added for the radius-system namespace deletion scenario, including:

• Step-by-step guidance for users facing this problem
• How to check for remaining resources
• How to force delete stuck resources
• How to interpret error messages such as "Discovery failed for some groups" and "Failed to delete all resource types"

Difference between rad uninstall kubernetes --purge and without --purge

Add a section explaining:

• What happens when running rad uninstall kubernetes --purge vs. without --purge
• What data and resources are left behind when not running with --purge (e.g., some CRDs, persistent data, configmaps, or other resources)
• Best practices for users who want a complete clean-up

Where should the new material be placed?

Suggest placement in the Kubernetes installation and management docs, under troubleshooting or FAQ sections.

The associated pull request from the Radius code repo, if applicable

Reference issue: https://github.com/radius-project/radius/issues/10255

Additional context

See the linked issue for details, example output, and observed behavior. This update will help users avoid confusion and successfully clean up resources when uninstalling Radius.

AB#17132

Start by reading the linked Radius issue 10255 and the existing Kubernetes installation and management documentation to confirm the deletion behavior and current uninstall guidance. Add a troubleshooting section covering stuck resources, remaining pods, discovery errors, force deletion, and a comparison of rad uninstall kubernetes --purge with the default command; done means users can follow the steps to diagnose and complete cleanup.