Add routed PSU carrier board layout (rev 0.1)

- Placement script (layout_pcb.py): LV left, HV right, panel connector on the
  boundary, terminal blocks on the edges, heatsink space for the TO-220s
- Freerouting-based routing script (route_pcb.py) that routes with oversized
  tracks/vias and shrinks them, giving 3 mm HV-to-LV and 1.3 mm HV-to-HV
- Custom DRC rules (plasma_dmd_psu.kicad_dru) with documented exceptions
- Wide TO-92 footprints; schematic generator now keeps symbol UUIDs
- DRC: 0 violations, 0 unconnected pads, schematic parity OK

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -20,7 +20,7 @@ Stern/Sega display PSU (520-5138-00). The original transformer and AC front end
 |---|---|
 | [docs/power-supply.md](docs/power-supply.md) | PSU design: block diagram, analysis of the original board, changes |
 | [hardware/psu-schematic.svg](hardware/psu-schematic.svg) | PSU schematic (generated by [hardware/psu_schematic.py](hardware/psu_schematic.py)) |
-| [hardware/kicad/](hardware/kicad/) | KiCad 10 project for the PSU carrier board (schematic + net classes, PCB not started) |
+| [hardware/kicad/](hardware/kicad/) | KiCad 10 project for the PSU carrier board: schematic and routed PCB (rev 0.1) |
 | [docs/safety.md](docs/safety.md) | Safety design (HV watchdog, fusing, layout, bring-up procedure) |
 | [docs/esp32-interface.md](docs/esp32-interface.md) | ESP32 pin plan, 74HCT245 level shifter, panel signals |
 | [docs/bom.md](docs/bom.md) | Bill of materials |
@@ -32,7 +32,8 @@ Stern/Sega display PSU (520-5138-00). The original transformer and AC front end
 - [ ] Identify panel: manufacturer/part number from its label
 - [ ] Map the panel's power connector pins (WPC panel ≠ Stern CN2 pinout) and check if +12 V is used
 - [ ] Map the panel's 14-pin data connector
-- [ ] Lay out the PSU PCB in KiCad ([hardware/kicad/](hardware/kicad/README.md))
+- [x] Lay out the PSU PCB in KiCad ([hardware/kicad/](hardware/kicad/README.md))
+- [ ] Review the PCB and work through the [before ordering](hardware/kicad/README.md#before-ordering) checklist
 - [ ] Order parts ([docs/bom.md](docs/bom.md))
 - [ ] Build and bench-test the PSU **without the panel** ([bring-up](docs/safety.md#bring-up-procedure))
 - [ ] Build HV watchdog and verify that the relay drops when toggling stops