Fix layout geometry documentation (outer columns y-offset)

[Matthew-Grayson]

Summary

Documentation shows the outer columns (far-left and far-right key columns) as being lower than they are on a physical Advantage360.

Problem

• info.json implies that the outer columns are at the same y alignment as the column next to it ( The keys '=', and '1', are both described as being at 0.25y).
• key-positions.png should visually match the corrected geometry.

Scope

1. Update info.json:

   • Raise each key in the outer columns by 0.125u (subtract 0.125 from y for those keys).
   • Ensure both left-most and right-most outer columns are adjusted.
   • Keep all other keys unchanged.

2. Update key-positions.png:

   • Raise the outer columns by 1/8 key (0.125u) so the diagram matches info.json.

Motivation

I'm calculating a typing effort grid for the Advantage360 that takes into account its concavity. I planned to use the numbers from info.json as a starting point but noticed they don't match the physical keyboard.