draw_box_border() (vt100.c) strokes four 1px edges around the 640x480
CANVAS box, reusing the same border-gray constant the REPL strip's
border lines use (renamed VT100_STRIP_BORDER_GRAY -> VT100_BORDER_GRAY
since it's now shared -- one pinned color decision, 4.4w, not two).
Called from erase_display()'s box-scoped branch so the border survives
every box clear (the initial one and any later ESC[2J), not just the
first.
Verified: three-arch clean QEMU boot + logs, amd64 screendump showing a
full rectangle outline around the box, visually distinct from the strip
below it.
Punch list §25 item 4.4z complete.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
