shouldBeOnEdgeOfBoard prop typechecks but is never consumed by the auto-placer

[gsdali]

Summary

shouldBeOnEdgeOfBoard is declared on pcbLayoutProps (so every
component that extends those layout props — chips, resistors, caps,
diodes, plated holes, etc.) and shows up in TypeScript completion,
but the runtime never reads it. Setting it on a component is a
no-op today.

$ rg 'shouldBeOnEdgeOfBoard' /path/to/tscircuit/core/lib/
# (no results — the prop is parsed by zod but never consumed)

This is the same shape of bug as #2242 (pcbPositionMode typechecks
but unused, fixed in #2247) and #2270 (<platedhole connectsTo>
typechecks but disconnected) — a documented prop the runtime ignores.

Repro

<board width="40mm" height="14mm">
  {/* User declares "this part must end up on the board edge". */}
  <chip
    name="J_USB"
    shouldBeOnEdgeOfBoard
    footprint={...usb-c receptacle...}
    connections={...}
  />
  <resistor name="R1" resistance="10k" footprint="0402" />
  <resistor name="R2" resistance="10k" footprint="0402" />
</board>

Expected: the auto-placer constrains J_USB to a position where its
courtyard touches a board edge.

Actual: prop has no observable effect; J_USB packs interior with
the resistors based on the default packPlacementStrategy.

Why it matters

This is the missing knob for the most common manual-placement task on
real boards: connectors and through-holes that must reach the
board edge so cables can plug in or wires can be soldered. Today the
workaround is to hand-place every edge-mounted part with explicit
pcbX/pcbY (we ended up doing this for ~9 components on a 45×14 mm
board); a working shouldBeOnEdgeOfBoard would let users delegate
the X/Y picking to the packer for the parts that don't care about
specific position, only "must be on an edge".

Suggested fix shape

Two-repo change. Sketch:

1. tscircuit/calculate-packing — add mustBeOnBoundary?: boolean
   (or similar) to InputComponent. The PackSolver2 candidate-scorer
   already considers the board outline; for components flagged this
   way, candidate positions whose courtyard doesn't touch the
   boundaryOutline are excluded.

2. tscircuit/core — in
   Group_doInitialPcbLayoutPack.ts, when building the PackInput
   for the solver, propagate _parsedProps.shouldBeOnEdgeOfBoard
   from each child onto the corresponding InputComponent entry.

A "nearest of any edge" semantics is the simplest first cut. Future
extension: shouldBeOnEdgeOfBoard: "left" | "right" | "top" | "bottom" | true for finer control.

Workaround until fixed

Set explicit pcbX/pcbY on every edge-anchored part. For boards with
many connectors / through-holes this is the bulk of the manual
placement work.