Ensure prompt output consistently uses stderr in raw-TTY mode

[coderabbitai]

Currently, prompt.run configures huh.Form.WithOutput(streams.ErrOut) only for accessible-mode prompts. In raw-TTY mode, the form uses huh's default TUI output stream, despite the prompt.IO documentation stating that prompts go to ErrOut.

Use huh.Form.WithOutput(streams.ErrOut) unconditionally.

Backlinks

• Source PR: feat!: CLI v2 #43
• Review discussion: feat!: CLI v2 #43 (comment)