test: add pcb snapshot for polygon smtpads with coveredWithSolderMask

[ETwithin]

Summary

Adds a PCB snapshot test demonstrating that polygon-shaped smtpads correctly:

1. Propagate is_covered_with_solder_mask: true in circuit-json output
2. Render with the solder mask layer visible via showSolderMask: true

Test Details

The test uses a 5-pad capacitive touch slider layout (short → tall → short) matching the design from tscircuit/tscircuit#786:

const pads = [
  { name: "PAD1", pcbX: -8, width: 2.5, height: 6 },
  { name: "PAD2", pcbX: -4, width: 2.5, height: 8 },
  { name: "PAD3", pcbX:  0, width: 2.5, height: 10 },
  { name: "PAD4", pcbX:  4, width: 2.5, height: 8 },
  { name: "PAD5", pcbX:  8, width: 2.5, height: 6 },
]

Each pad uses shape="polygon" with coveredWithSolderMask={true}.

Assertions

• All 5 pcb_smtpad elements have is_covered_with_solder_mask: true
• All pads retain shape: "polygon" and points array in circuit-json
• PCB snapshot renders with solder mask layer visible

Related

• Closes (partial): Support Capacitive Touch Slider element, add solvermask support to smtpad, document capacitive touch element tscircuit#786
• Companion PR to docs tutorial: docs: add capacitive touch slider tutorial docs#486

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Project	Deployment	Actions	Updated (UTC)
tscircuit-core-benchmarks	Ready	Preview, Comment	Mar 1, 2026 8:21am

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