Notebook does not respect output rendering settings

[Tyrrx]

Describe the bug

When settings the output rendering to plain text the notebook still shows it as a custom component:

In Host mode the error text is not outputted as string:

When running e.g. Helmfile, which prints to std error, the output is basically not usable because it's too verbose.

Please complete the following:

Which version of .NET Interactive are you using? (In a notebook, run the #!about magic command. ):

• OS
  • Windows 11
  • Windows 10
  • macOS
  • Linux (NisOS 25.05)
  • iOS
  • Android
• Browser
  • Chrome
  • Edge
  • Firefox
  • Safari
• Frontend
  • Jupyter Notebook
  • Jupyter Lab
  • nteract
  • Visual Studio Code
  • Visual Studio Code Insiders
  • Visual Studio
  • Other (please specify)

Screenshots