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>

tests/README.md

@@ -289,3 +289,18 @@ Button positions (relative to canvas):
 
 - **Timer tests**: May fail due to timing sensitivity
 - **Tree tests**: Button click positions may vary
+
+## Open tasks
+
+- **Research: are the Asyncify fiber shims still needed under native-EH?** Two
+  `scripts/common/inject-dyncall-shims.sh` fixes — the fiber trampoline self-heal
+  (§3c) and the nested-Asyncify handleSleep save/restore (§3) — were written for the
+  legacy-EH *park-throw* model. Under native wasm-EH the top loop is a per-frame-yield
+  while-loop with no park-throw, so ablating either shim
+  (`SHIM_DISABLE_TRAMPOLINE_HEAL` / `SHIM_DISABLE_HANDLESLEEP`, wired in
+  `tests/apps/Makefile.wasm`) no longer reproduces the disease it guarded — the old
+  red "ablation pins" in `asyncify/asyncify-races.spec.ts` have been flipped to
+  green "shim-redundancy pins" that now prove the native-EH path stays clean *with the
+  shim ablated*. **To do:** sweep the real apps (modals, nested fibers, long sleeps,
+  pthread pool) with each shim ablated; if all stay green, drop the shim injection and
+  these pins. Until proven, they stay injected (belt-and-suspenders).