Fix SOT-25 pad-row width handling

[Abse2001]

Motivation

C156283 (APX823-26W5G-7, SOT-25-5) could not be reproduced accurately because the SOT-25 generator ignored its w parameter and always placed pad rows at fixed positions.

Implementation

• Use w as the center-to-center span between SOT pad rows.
• Preserve existing default SOT-23/SOT-25 geometry by updating the default span value.
• Make SOT-23 and SOT-25 honor the existing rounded parameter.
• Add a real C156283 SOT-25 regression footprint using its measured pad dimensions and rounded0.
• Update affected SOT-23 SVG snapshots for the corrected custom-width behavior.

Validation

• bun test tests/sot23.test.ts tests/sot25.test.ts
• bun run build