surf scroll: add positional direction/amount shorthand

[SeMmyT]

Problem

Scrolling requires verbose flags: surf scroll --scroll-direction down --scroll-amount 8. AI agents burn tokens on this boilerplate.

While scroll.top, scroll.bottom, scroll.to, scroll.info exist as dot-commands, the common case of scrolling by pixel amount in a direction is missing as a shorthand.

Proposed fix

Add positional argument parsing for scroll:

surf scroll down 800       # scroll down 800px
surf scroll up 400         # scroll up 400px
surf scroll bottom         # scroll to page bottom
surf scroll top            # scroll to page top

Also return scroll position in output:

Scrolled to Y:800 (page height: 3200)

Severity

Medium — high token waste for AI agents.