debug: dump prompt cell styling for both prompt glyphs (#110)

PTY debug dumps now print per-cell dim attributes for the input row.
They detect the prompt glyph actually on the row, so Codex's Ultra `»`
prompt is covered alongside `›`. Before, only `›` was checked, and it
matched anywhere in the line.

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Co-authored-by: aannoo <aannoo@users.noreply.github.com>