KiCad 10's kicad-cli has no specctra subcommands, kipy has no Specctra
support, and pcbnew.ImportSpecctraSES needs a GUI display. This adds a
pure-Python applier that injects FreeRouting's routed wires and vias
directly into a .kicad_pcb, reusing the existing sexp_tree engine.
Reads the (resolution unit value) scope for scaling, applies the
Specctra Y-up to KiCad Y-down flip, maps SES net names to board net
numbers, and splices (segment)/(via) nodes in before the board's
closing paren so the rest of the file is preserved byte-for-byte.
Fixtures are a real Arduino_Mega template board and a FreeRouting-routed
SES; the integration test applies 23 segments across GND and +5V.