fix(highway_3d): recover from WebGL context loss instead of crashing on alt-tab (#790)

Switching the active window / alt-tabbing away (most often on Windows) can
trigger a GPU context reset. The 3D highway's WebGL renderer had no
webglcontextlost handler, so a lost context was left to escalate into a
render-process crash -- matching the intermittent "randomly crashes when I
change windows" desktop reports.

The renderer now binds webglcontextlost/webglcontextrestored on its own WebGL
canvas (ren.domElement): the loss is preventDefault()'d so the browser keeps the
context restorable, draw() bails while the context is down so no GL work runs on
a dead context, and on restore the viewport is re-applied and rendering resumes
(Three re-uploads scene resources on the next frame). Listeners are removed in
teardown.

Root cause is a strong hypothesis -- the crash is intermittent and
unreproducible -- but the fix is low-risk and additive and closes a real gap:
there was no context-loss handling anywhere in the renderer.

plugins/highway_3d 3.31.2 -> 3.31.3. Tests:
tests/js/highway_3d_context_loss.test.js (source-contract, like the other
highway_* tests). The sibling keys_highway_3d / drum_highway_3d renderers share
the same gap -- follow-up in their repos.


Claude-Session: https://claude.ai/code/session_01UR2Cr7GEu3yMY7SrfxH6c1

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

plugins/highway_3d/plugin.json

@@ -1,7 +1,7 @@
 {
     "id": "highway_3d",
     "name": "3D Highway",
-    "version": "3.31.2",
+    "version": "3.31.3",
     "type": "visualization",
     "bundled": true,
     "script": "screen.js",