chore(outputs): regenerate STEP and PCBWay fabrication package

* firstpcb.step regenerated from current PCB (DRC-clean board with
  four M2 mounting holes). Two component 3D models (R_0805 and
  JST_XH_B4B-XH-A) fail to decompress under the Nix-packaged KiCad;
  affected components are missing 3D shapes but board body and other
  models are present.
* pcbway_export/ contains gerbers (RS-274X Protel, 4.6 mm), separate
  PTH/NPTH Excellon drill files, drill maps, gbrjob, and a README
  with the stackup/spec.
* firstpcb_pcbway.zip is the upload-ready archive for PCBWay.
* .gitignore updated to drop KiCad autosaves and *.pre-drc-fix locals.

Constraint: PCBWay accepts gerbers with Protel extensions and Excellon
  drills, separate PTH/NPTH preferred
Directive: regenerate this package whenever the PCB changes -- the zip
  is a derived artifact; the source of truth is firstpcb.kicad_pcb

pcbway_export/firstpcb-PTH.drl

@@ -0,0 +1,105 @@
+M48
+; DRILL file KiCad 10.0.0 date 2026-05-15T16:38:18
+; FORMAT={-:-/ absolute / metric / decimal}
+; #@! TF.CreationDate,2026-05-15T16:38:18-04:00
+; #@! TF.GenerationSoftware,Kicad,Pcbnew,10.0.0
+; #@! TF.FileFunction,Plated,1,2,PTH
+FMAT,2
+METRIC
+; #@! TA.AperFunction,Plated,PTH,ViaDrill
+T1C0.300
+; #@! TA.AperFunction,Plated,PTH,ComponentDrill
+T2C0.300
+; #@! TA.AperFunction,Plated,PTH,ComponentDrill
+T3C0.800
+; #@! TA.AperFunction,Plated,PTH,ComponentDrill
+T4C0.900
+; #@! TA.AperFunction,Plated,PTH,ComponentDrill
+T5C0.950
+%
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