refactor: collapse dual-mode plumbing — the DOM port is the only WASM build

The canvas (wxUniversal) mode is gone (wxwidgets submodule); remove every
piece of side-by-side plumbing so there is exactly one build and one test
flow:

- scripts/build-wxuniversal-wasm.sh -> scripts/build-wx-wasm.sh; no
  --dom/--enable-universal; builds into build-wasm/wxwidgets
- build-wasm-test.sh: no DOM_BUILD / apps-dom rsync mirror / PORT=dom;
  apps build straight into tests/apps (Makefile.wasm PORT conditionals
  collapsed; wx.js + wx-dom.js always pre-js)
- docker/build.sh, build-kicad-target.sh, env.sh: WX_PORT / -dom /
  -universal suffixes removed; kicad builds to kicad-<app>, outputs to
  output/; wx.js/wx-dom.js copied from the real source path
  (/workspace/wxwidgets/build/wasm — the old build-wasm path never
  existed and silently failed)
- setup-kicad-wasm.sh: single target dir; the perl wx-dom.js injection is
  gone — the 7 checked-in kicad pages now reference wx-dom.js directly
- playwright configs serve apps/; fixtures drop the test-results/dom and
  logs/wxwidgets/dom namespacing; boot.spec asserts wxDomPort
  unconditionally; pcbnew.spec uses one reference image;
  appearance.spec assertions unconditional
- compare/update-baseline-screenshots.sh: --port removed
- tests/gal-regression/wasm/Makefile: links build-wasm/wxwidgets and
  carries wx-dom.js as a second pre-js — the gal-webgl suite (30 specs)
  now actually builds and runs here (it needed host-side boost+glm via
  scripts/deps; the bundle had been missing, timing the whole spec out)
- tests: clickCanvas() dispatches via page.mouse (DOM widgets
  legitimately cover the canvas; locator actionability refused the
  click); the comprehensive spec drives wxChoice through its native
  <select> (browser-owned popup cannot be coordinate-clicked)
- docs: README/CLAUDE.md/build.md script names and dirs;
  features/wx-dom-port README reframed (DOM is THE port), visual-notes
  bugs 26-28; FindwxWidgets.cmake config label drops 'wasmuniv'
- wxwidgets submodule -> 9dbacc9448 (DOM-only port, fork diff shrunk)

Gate: full wx e2e suite 292 passed / 1 skipped / 0 failed — first run
ever with the gal-webgl specs green (28 scenarios + load + sequential).

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

tests/apps/Makefile.wasm

@@ -8,16 +8,8 @@
 TOOLS_ROOT = ../../wxwidgets/build/wasm
 KICAD_ROOT = ../../kicad
 
-# PORT=dom links against the DOM (non-universal) wxWidgets build and adds the
-# wx-dom.js shim. Invoked by scripts/build-wasm-test.sh --dom from a mirrored
-# source tree in tests/apps-dom (so canvas and DOM bundles coexist).
-ifeq ($(PORT),dom)
-    WXCONFIG = ../../build-wasm/wxwidgets-dom/wx-config
-    WXLIB_PREFIX = libwx_wasmu
-else
-    WXCONFIG = ../../build-wasm/wxwidgets-universal/wx-config
-    WXLIB_PREFIX = libwx_wasmunivu
-endif
+WXCONFIG = ../../build-wasm/wxwidgets/wx-config
+WXLIB_PREFIX = libwx_wasmu
 
 CXX = em++
 WX_CXXFLAGS := $(shell $(WXCONFIG) --cxxflags)
@@ -113,25 +105,16 @@ LDFLAGS_COROUTINE = $(DEBUG_LDFLAGS) $(COROUTINE_BASE_LDFLAGS) $(WX_LDFLAGS_NOGL
 # forbids the very multi-parked-sleep states the harness exists to exercise.
 LDFLAGS_RACES = $(DEBUG_LDFLAGS) $(COROUTINE_BASE_LDFLAGS) -sASSERTIONS=0 $(WX_LDFLAGS_NOGL)
 
-# In dom mode a second pre-js carries the DOM-control shim ("--pre-js A --pre-js B"
+# A second pre-js carries the DOM-control shim ("--pre-js A --pre-js B"
 # after expansion — emcc accepts repeated --pre-js).
 # JS_FILES lists the actual pre-js paths (no flags) so the link targets can
 # depend on them — otherwise editing a shim wouldn't trigger a relink.
-ifeq ($(PORT),dom)
-    JS = $(TOOLS_ROOT)/wx.js --pre-js $(TOOLS_ROOT)/wx-dom.js
-    JS_FILES = $(TOOLS_ROOT)/wx.js $(TOOLS_ROOT)/wx-dom.js
-else
-    JS = $(TOOLS_ROOT)/wx.js
-    JS_FILES = $(TOOLS_ROOT)/wx.js
-endif
+JS = $(TOOLS_ROOT)/wx.js --pre-js $(TOOLS_ROOT)/wx-dom.js
+JS_FILES = $(TOOLS_ROOT)/wx.js $(TOOLS_ROOT)/wx-dom.js
 HTML = $(TOOLS_ROOT)/template.html
 
 # wxWidgets library directory - used as dependency to rebuild when libs change
-ifeq ($(PORT),dom)
-    WX_LIB_DIR = ../../build-wasm/wxwidgets-dom/lib
-else
-    WX_LIB_DIR = ../../build-wasm/wxwidgets-universal/lib
-endif
+WX_LIB_DIR = ../../build-wasm/wxwidgets/lib
 # Key library that changes when wxWidgets is rebuilt
 WX_CORE_LIB = $(WX_LIB_DIR)/$(WXLIB_PREFIX)_core-3.2-emscripten.a