fix(cli): only pad short responses to avoid pushing content off-screen

[gnanam1990]

Summary

• Unconditional half-terminal-height padding after every response (added in fix(cli): anchor input prompt near bottom of terminal after responses #4359, removed in fix(cli): pin entire TUI to bottom of terminal on startup #4412) caused long responses to be scrolled out of view
• Re-introduces post-response padding but gates it on response length: padding only fires when the response is shorter than half the terminal height
• Computes the exact gap (_pad - _resp_lines) so no unnecessary blank lines are added

How it works

_terminal_lines = shutil.get_terminal_size().lines
_pad = _terminal_lines // 2
if _pad > 2:
    _resp_lines = _chat_response.count("\n") + 1 if isinstance(_chat_response, str) else 1
    if _resp_lines < _pad:
        _actual_pad = max(1, _pad - _resp_lines)
        _cprint("\n" * _actual_pad)

• Short response → prompt is anchored near the bottom ✓
• Long response → no padding, content stays on screen ✓

Fixes #4421

Test plan

• Short response (e.g. "What is 2+2?") — blank padding appears after response, prompt sits near bottom
• Long response (e.g. "Explain TCP/IP in detail") — no padding, response not pushed off-screen
• python3 -m py_compile cli.py passes with no errors

🤖 Generated with Claude Code

[teknium1]

Thanks for the contribution @gnanam1990! This is a thoughtful approach to gating the padding on response length.

However, the underlying issue (#4421) was already resolved by PR #4412 (merged ~20 minutes before the issue was filed). That PR removed the per-response padding entirely and replaced it with a one-time startup scroll that pins the TUI to the bottom of the terminal. The padding code from #4359 that #4421 describes no longer exists on current main.

Closing as the root cause is already addressed. Appreciate you taking the time!