Migrates SearchState.input from String to InputBuffer so wide-char (Hangul/CJK) keystrokes advance the terminal cursor by display columns instead of char count. Adds cursor placement in render_input_bar via f.set_cursor_position and a Hangul round-trip pin in tests/search.rs. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>