feat(wasm-eh): migrate the WASM build to native wasm exceptions (+ 3D viewer default-on)

Replace the legacy Emscripten JS-exceptions model with native wasm-EH (legacy
encoding) across the whole build, keeping Asyncify coroutines working via a
from-source Binaryen --hoist-cpp-catches pre-pass. Net result: native-EH is the
only build mode, the 3D viewer is on by default, and pcbnew shrinks substantially.

Highlights:
- Binaryen submodule everywhere + --hoist-cpp-catches integration in apply-asyncify;
  post-link Asyncify covers every app wasm (not just standalone test wasm).
- Build deps (incl. OpenCASCADE without OCC_CONVERT_SIGNALS) and all KiCad apps
  with -fwasm-exceptions; emscripten_sleep added to the post-link asyncify-imports.
- libcontext fiber entry wired under native exceptions; while-loop main loop +
  currData shim injected into all wx apps.
- Native-EH collab apply fixed: DEBUG-define the embind TU + match all out-of-CMake
  C++ TUs' ABI flags to the core, fixing the vtable-layout skew / mis-dispatch.
- 3D viewer enabled by default (real raytracer linked, not the stub).
- Retire the EH-spike scaffolding; flip the asyncify-races ablation pins to
  shim-redundancy pins (native-EH stays clean with the legacy shims ablated).
- Fix the asyncify-races quiescence check to not require Asyncify.currData==0:
  under the native-EH per-frame-yield top loop the main stack is asyncify-suspended
  every frame, so currData legitimately churns (a freed-but-not-yet-nulled buffer,
  not a leak). Refresh the pcbnew toolbar screenshot baseline for the new kicad.
- CI: drop the obsolete binaryen_version input/env (the build uses the binaryen
  submodule fork's wasm-opt, not a version download); key the wasm-output cache on
  the binaryen submodule SHA instead.

Bumps the wxwidgets + binaryen submodules to their squashed feature commits.

Validated green: all 7 apps native-EH (real 3D in pcbnew); KiCad e2e 63/63
Firefox + Chromium (3D viewer renders); wx 336; coroutine 34/34 both engines;
asyncify 7/7 both engines.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docker/Dockerfile

@@ -25,10 +25,13 @@ RUN apt-get update && apt-get install -y \
     unzip \
     && rm -rf /var/lib/apt/lists/*
 
-# Install emsdk from source (same approach as scripts/setup-emsdk.sh)
-# EMSCRIPTEN_VERSION must match scripts/common/versions.sh
-ARG EMSCRIPTEN_VERSION=4.0.2
-RUN git clone https://github.com/emscripten-core/emsdk.git /emsdk \
+# Install emsdk from source (same approach as scripts/setup-emsdk.sh). The version is the SINGLE
+# source of truth in scripts/common/versions.sh, passed in as a build arg by docker/build.sh (via the
+# compose build.args). Do NOT hardcode it here — fail fast if the arg is missing so a stale image can
+# never silently use the wrong toolchain.
+ARG EMSCRIPTEN_VERSION
+RUN test -n "${EMSCRIPTEN_VERSION}" || { echo "EMSCRIPTEN_VERSION build-arg required (scripts/common/versions.sh)"; exit 1; }; \
+    git clone https://github.com/emscripten-core/emsdk.git /emsdk \
     && cd /emsdk \
     && ./emsdk install ${EMSCRIPTEN_VERSION} \
     && ./emsdk activate ${EMSCRIPTEN_VERSION}