fix(cli): handle CJK wide chars in TUI input height

[qaqcvc]

Summary

• fix multiline TUI input height calculation for CJK / East Asian wide characters
• use prompt_toolkit.utils.get_cwidth() instead of len() when estimating wrapped input rows
• prefer prompt_toolkit's live terminal width over shutil when the TUI app is running
• add regression tests covering wide-character wrapping behavior

Root cause

The TUI input box estimated visual line count using Python character length, but prompt_toolkit renders many CJK characters as double-width terminal cells. Once the input wrapped, Hermes undercounted the number of visual rows, so the first row could get visually overwritten/disappear.

Testing

• python3 -m pytest tests/test_cli_status_bar.py -q -o addopts=''
• python3 -m pytest tests/test_cli_status_bar.py tests/test_cli_init.py tests/test_cli_loading_indicator.py -q -o addopts=''

Closes #5221

[teknium1]

Merged via PR #5665. Your commit was cherry-picked with authorship preserved. Thanks @qaqcvc!