Check traces against copper pours

[ShiboSoftwareDev]

Fix

Stacked on #206.

Adds shape-aware trace clearance/contact checks for rectangular, polygon, and BREP copper pours. The check:

• reports different-net overlap and below-minimum-clearance errors
• uses curved BREP ring geometry
• preserves BREP inner rings as copper-free voids
• ignores same-net trace/pour contact
• is included in checkEachPcbTraceNonOverlapping and exported as a standalone check
• updates the visual snapshot to show the collision marker and message

Checks

• full suite: 180 tests passed, 6 snapshots
• bunx tsc --noEmit
• bun run build
• fixed visual snapshot inspected