solderjumper without a pin count emits NaN geometry

Summary

fp.string("solderjumper") with no pin count silently emits invalid geometry instead of a real footprint. solderjumper2 and solderjumper3 are fine.

Reproduction

import { fp } from "@tscircuit/footprinter"

const circuitJson = fp.string("solderjumper").circuitJson()
console.log(circuitJson.find((e) => e.type === "pcb_courtyard_rect"))
console.log(circuitJson.find((e) => e.type === "pcb_silkscreen_text"))

Output at v0.0.417:

• 0 pads
• pcb_courtyard_rect with width: NaN and center.x: NaN
• pcb_silkscreen_text with anchor_position.x: NaN

fp.string("solderjumper2") and fp.string("solderjumper3") return 2 and 3 pads with finite geometry.

Cause

In src/fn/solderjumper.ts, num_pins is read from params with no default. A bare solderjumper string parses to num_pins: undefined, so (num_pins - 1) * padSpacing and every value derived from it (outline, courtyard, silkscreen anchor) become NaN.

Expected

A bare solderjumper should render a real footprint. Most footprints that take a pin count default a sensible one when it is omitted (dip, ssop, pinrow and many others). A couple throw a clear error instead (jst). Either is fine. Emitting NaN is not.

Start in src/fn/solderjumper.ts and trace how the missing pin count reaches pad spacing, outline, courtyard, and silkscreen geometry. Compare the behavior with solderjumper2 and solderjumper3, then verify that a bare solderjumper produces a valid footprint with finite geometry and a nonzero pad count, or reports a clear error.