[FEATURE]: configurable opening prompt size presets and overrides in TUI home

[dmoliveira]

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

The opening TUI prompt on the home screen is too constrained for long planning prompts, making it hard to keep context while typing.

Problem

• Home prompt width is effectively compact by default and not user-adjustable.
• Input height is limited for long prompts.
• Users need a simple way to choose a larger composer for planning-heavy workflows.

Proposal

Add tui.initial_prompt configuration with:

• size: compact | medium | large
• width_percent: optional override (40-100)
• height_percent: optional override (10-60)

Behavior expectations

• compact preserves current behavior.
• medium and large provide more visible context.
• Settings apply to the opening home prompt flow.

Acceptance criteria

• Config schema supports the new fields and validates ranges.
• Home prompt sizing responds to presets and overrides.
• Docs and generated API/SDK artifacts are updated.
• Tests cover config validation paths.

[github-actions]

This issue doesn't fully meet our contributing guidelines.

What needs to be fixed:

• Feature requests require the *[FEATURE]: prefix in the title. Please update the title to start with [FEATURE]:
• Feature requests must include a verification checkbox confirming the feature hasn't been suggested before (see Feature Request template)

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[dmoliveira]

Updated this issue to match the feature template (title now starts with [FEATURE]: and includes the required verification checkbox + detailed description/acceptance criteria). I don't have permission to remove the label from this upstream repo—could a maintainer please clear that label?

[github-actions]

This issue has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.

Feel free to open a new issue that follows our issue templates.