Add extensionless regression test files for tclsh, wish, and expect
shebangs so syntect bumps don't silently break first-line detection.
Move changelog entry from Features to Syntaxes per reviewer suggestion.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Control characters displayed in caret notation (e.g. ^@ for NUL)
occupy 2 terminal columns, but the width calculation treated them
as 0-width. Add a char_width() helper that returns 2 for control
characters, fixing incorrect line wrapping with --binary=as-text.
Fixes#3631
Matt Van Horn