/claim #40

I implemented ViaGridBoard support for tscircuit based on the Opulo ViaGrid spec.

What I added:

• ViaGridBoard component with small/medium/large presets
• Custom row/col support for any size needed
• Fixed the via dimensions to match ViaGrid spec (0.6mm drill, 1.2mm pad instead of 0.8/1.6)
• Changed pin labels to proper format (A1, A2, B1, B2 instead of V1, V2, V3)
• Added multiple test files to show different configurations
• Kept 2.54mm pitch for breadboard compatibility

The board margins are now 3mm as per ViaGrid standard. Works just like other boards in the repo - you can pass size=“medium” or go custom with specific rows/cols.