Add Gerber-based PCB short circuit detection

[Abse2001]

Motivation
Shorts can be introduced or missed if we only inspect pre-Gerber circuit JSON geometry. This check validates the copper geometry that is actually emitted for fabrication, including traces, pads, vias, plated holes, and copper pours.
Implementation
Added tsci check short [file].
Generates Gerber ZIP output for the checked board.
Reconstructs copper primitives from Gerber commands:aperture flashes
stroked traces
filled regions
copper-pour clear regions/cutouts

Detects same-layer intersections between copper assigned to different nets.
Adds Gerber X2 net metadata using %TO.N,% / %TD.N%.
Uses X2 net metadata during analysis when present.
Falls back to circuit-json geometry matching for object/net association.
Splits short-check registration, analysis, and geometry helpers into dedicated files following CLI command conventions.

[seveibar]

Needs rewrite

• reimplementing a ton of geometry checks and gerber types
• implementation for this lives in cli without robust testing
• No bitmap based testing
• Any new shapes etc require new implementation

Do this:
Create repo called check-shorts
Implement robust repros
Use circuit-to-canvas and do “bitmap coloring” using pcb_port and connectivity map keys. If you ever have to recolor with a connectivity map key then you have a short
Include a gerber mode which internally creates RASTERIZED gerbers