feat: pass the wheel up from a table that cannot move #178

What

#164 made a scroll region leave the wheel for the region around it when it cannot move that way. A table keeps its own wheel handling (table.end, table.mach:916) and still takes the wheel at its limit or with nothing to scroll, on both axes, so a table inside a scrolling dock stalls the dock under the pointer.

Acceptance

• A table takes the vertical wheel only when it can move vertically that way, and the horizontal wheel only when it can move horizontally that way, passing the rest to the enclosing region
• A test covers a table inside a scrolling dock at both ends of its range, on both axes