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>

scripts/common/env.sh

@@ -36,6 +36,15 @@ export WX_BUILD="$BUILD_ROOT/wxwidgets"
 # Emscripten settings
 export EMSDK_QUIET=1
 
+# Exception model for ALL WASM translation units — the C/C++ dependencies, wxWidgets, and KiCad
+# (build-wx-wasm.sh and build-kicad-target.sh source this file and reuse DEPS_EH_FLAGS). Native
+# WebAssembly exceptions (legacy binary encoding) are the only build mode. -sSUPPORT_LONGJMP=wasm is
+# required because the deps that use setjmp/longjmp (freetype, cairo, OpenCASCADE) must use wasm
+# setjmp — emscripten's JS-longjmp implementation cannot coexist with -fwasm-exceptions (it would
+# leave emscripten_longjmp undefined). -sWASM_LEGACY_EXCEPTIONS=1 selects the EH binary encoding our
+# post-link Asyncify + catch-arm-hoisting pass can consume (Asyncify can't handle exnref).
+export DEPS_EH_FLAGS="-fwasm-exceptions -sSUPPORT_LONGJMP=wasm -sWASM_LEGACY_EXCEPTIONS=1"
+
 # Emscripten SDK setup
 # If EMSDK is already set (e.g. Docker entrypoint sourced emsdk_env.sh), use it.
 # Otherwise auto-install a local copy under tools/emsdk/.