Summary

Adds small but high-impact quality-of-life improvements to the terminal input area, all behind new tui config options with backward-compatible defaults.

Closes #10418
Closes #5626

What's new

1. Scrollbar in the input area

• TextArea now has scrollbar=True, making it easier to navigate long multi-line prompts.

2. Configurable input height

• New option: tui.input_max_lines (default: 8)
• Controls the maximum height of the input box. Users on larger terminals can increase it (e.g. 30) without the UI clipping.

3. Configurable large-paste collapsing

• New option: tui.collapse_large_pastes (default: true)
• When false, bracketed-paste and typing-detection paste collapsing is skipped entirely, which is useful for users who prefer inline pastes.

4. Optional "empty-input" guard for history navigation

• New option: tui.history_nav_requires_empty_input (default: false)
• When true, Up/Down arrows only browse history when the input buffer is empty; otherwise they move the cursor line-by-line. This matches the behavior of many terminal chat clients and prevents accidental history jumps while editing multi-line text.

5. Optional full input echo

• New option: tui.show_full_input (default: false)
• When true, the user's complete multi-line message is echoed back before the agent runs, instead of the compact ● first line (+N lines) preview.

Backward compatibility

Every default matches the current behavior, so existing users are unaffected. These are purely opt-in convenience knobs for power users.

Recommended setup to try

This is the config we run and the one that shows off the improvements best:

tui:
  input_max_lines: 30
  collapse_large_pastes: false
  history_nav_requires_empty_input: true
  show_full_input: true

Related context

These are quality-of-life settings common in other terminal chat interfaces (e.g. aichat, tg-cli, etc.) that users naturally expect to be available.