Add ScrollUp and ScrollDown as first-class tape commands that scroll
the terminal viewport by rows, with optional @time and repeat count.
Wire them through token keywords, parser command types, and command
execution using term.scrollLines(+/-1).
Update docs and fixtures to include the new commands in README, manual,
demo comments, and all.tape. Expand lexer/parser coverage and command
count assertions for the new command surface.
Fixes#404
Co-authored-by: Ayman Bagabas <ayman.bagabas@gmail.com>
Josh McKinney
bae3eb0b10