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>

README.md

@@ -14,7 +14,7 @@ git submodule update --init --recursive
 ./docker/build.sh
 
 # 3. Build wxWidgets for local testing
-./scripts/build-wxuniversal-wasm.sh
+./scripts/build-wx-wasm.sh
 
 # 4. Build wxWidgets test apps
 ./scripts/build-wasm-test.sh
@@ -29,7 +29,7 @@ npm run test:kicad    # KiCad tests (2 tests)
 
 ```bash
 # Requires: Node.js 18+ (Emscripten SDK auto-installed on first build)
-./scripts/build-wxuniversal-wasm.sh
+./scripts/build-wx-wasm.sh
 ./scripts/build-wasm-test.sh
 cd tests && npm install && npm test
 ```
@@ -48,7 +48,7 @@ kicad-wasm/
 │   ├── shims/              # Runtime JavaScript shims
 │   └── stubs/              # Stub implementations (libgit2, curl)
 ├── scripts/                # Build scripts
-│   ├── build-wxuniversal-wasm.sh   # Build wxWidgets for WASM
+│   ├── build-wx-wasm.sh   # Build wxWidgets for WASM
 │   ├── build-wasm-test.sh          # Build wxWidgets test apps
 │   ├── deps/               # Dependency build scripts
 │   ├── kicad/              # KiCad build scripts
@@ -98,7 +98,7 @@ Build standalone wxWidgets test apps for feature testing:
 
 ```bash
 # Build wxWidgets for WASM
-./scripts/build-wxuniversal-wasm.sh
+./scripts/build-wx-wasm.sh
 
 # Build test apps
 ./scripts/build-wasm-test.sh