fix(sot343): symmetrize pads to match KiCad SOT-343 (#667)

[yanyishuai]

Summary

Fixes the lopsided sot343 land pattern reported in #667.

Root cause

• Left pads used x: -p * 1.5 (after aligning to KiCad), but right pads used bare x: p, shifting the part off-center.
• Courtyard outline was similarly asymmetric.
• Number.parseInt(..., 4) for sot343_N used the wrong radix ("4" ? NaN).

Fix

• Use ?p * 1.5 for both pad columns (matches KiCad SOT-343_SC-70-4; courtyard IoU 100% / diff 0%).
• Mirror courtyard outline.
• Parse pin counts with radix 10.
• Add focused symmetry + parsing tests (no SVG matcher dependency).

Evidence

xs: [-0.825, -0.825, 0.825, 0.825]  // symmetric
KiCad courtyardDiffPercent: 0

Note vs earlier approaches

Keeping left at p*1.92 and only fixing the right side improves symmetry but fails KiCad parity (~15% courtyard diff). This PR prioritizes the repo's KiCad reference.

Fixes #667

[yanyishuai]

CI is green on 358010a (build/test/format-check/Format code all success).
Fix aligns sot343 pads to KiCad symmetry (±p*1.5) with courtyard mirror + IoU 100%.
Ready for review/merge when convenient.

[yanyishuai]

CI green — ready for review/merge on 358010a. Happy to address any feedback.

[yanyishuai]

Still CI-green and mergeable — gentle merge ping on 358010a. Happy to address any remaining feedback.

[yanyishuai]

Rebased onto latest main (kept cornerRadius). Pads ±p*1.5, mirrored courtyard, radix 10, KiCad IoU 100%. CI green on 2965ee2.

[yanyishuai]

Merge ping — CI green / mergeable=clean on 2965ee2 (sot343 symmetry). Please merge when convenient — payout blocked on merge.

[yanyishuai]

Merge-ready follow-up — CI green on #711 (Fixes #667 SOT-343 pad symmetry).

KiCad-aligned ±p*1.5, mirrored courtyard, radix-10 parse, symmetry tests + snapshots are in place. Branch is rebase-clean and mergeable.

Happy to address any remaining review notes immediately.

Wallet (if bounty payout applies): Do4v7foHJvRJLpRRoGaVPWX6DDEjX3yTK7J91gpwUQpE