Fix vf-eval non-TUI live overflow rendering

[snimu]

Description

When the terminal window wasn't high enough, the progress bar would render very poorly:

After this pr it looks good again:

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Test improvement

Testing

• All existing tests pass when running uv run pytest locally.
• New tests have been added to cover the changes

Checklist

• My code follows the style guidelines of this project as outlined in AGENTS.md
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

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Note

Low Risk
Small, localized change to terminal rendering configuration; main risk is minor formatting/visibility differences in edge-case terminal sizes.

Overview
Fixes Rich Live rendering in non-TUI mode by clamping vertical_overflow to "ellipsis" when screen=False, preventing oversized frames from scrolling and smearing repeated refreshes in small terminals. TUI/alternate-screen mode keeps vertical_overflow="visible" so full content can still render when space permits.

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