feat(wasm-dom): Phase 7 — KiCad pcbnew builds and runs on the DOM port

Pipeline: lexer generation (pcbcommon) ordered before the embind
pre-compile — a fresh-build-tree chicken-and-egg any new volume would
hit (generated pcb_lexer.h was included via -I${KICAD_BUILD}/common
before anything generated it). DOM flavor outputs flow through the
host-mounted output/dom/. pcbnew e2e on DOM: editor loads fully (layer
manager, toolbars, WebGL viewport, registry metrics), draw-lines test
passes; the header pixel-reference assertion fails as expected (native
DOM styling vs univ pixels) — port-aware references pending.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docker/build.sh

@@ -183,7 +183,7 @@ compile_app() {
     local out_dir="output"
     local kicad_build="kicad-${app}"
     if [[ "${WX_PORT:-}" == "dom" ]]; then
-        out_dir="output-dom"
+        out_dir="output/dom"
         kicad_build="kicad-${app}-dom"
     fi