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>

tests/js/highway_3d_context_loss.test.js

@@ -0,0 +1,45 @@
+// Contract test: 3D Highway WebGL context-loss recovery.
+//
+// Switching the active window / alt-tabbing (especially on Windows) can trigger
+// a GPU context reset. Without a handler the lost WebGL context escalates into a
+// render-process crash. The renderer owns its own WebGL canvas + heavy Three.js
+// lifecycle (too much to construct in a vm sandbox), so — like the other
+// highway_* source-contract tests here — this pins the wiring at the source
+// level: the loss must be preventDefault()'d (so the browser restores it), draw
+// must bail while lost, and the listeners must be torn down.
+
+const { test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const SCREEN_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'screen.js');
+const src = fs.readFileSync(SCREEN_JS, 'utf8');
+
+test('binds webglcontextlost + webglcontextrestored on the renderer canvas', () => {
+    assert.match(src, /ren\.domElement\.addEventListener\(\s*['"]webglcontextlost['"]/,
+        'must listen for webglcontextlost on ren.domElement (the WebGL canvas)');
+    assert.match(src, /ren\.domElement\.addEventListener\(\s*['"]webglcontextrestored['"]/,
+        'must listen for webglcontextrestored on ren.domElement');
+});
+
+test('the context-lost handler preventDefaults and pauses drawing', () => {
+    // Without preventDefault() the browser will not attempt to restore the
+    // context and the loss can escalate to a renderer crash.
+    const m = src.match(/_onCtxLost\s*=\s*\(e\)\s*=>\s*\{[\s\S]*?\};/);
+    assert.ok(m, '_onCtxLost handler must exist');
+    assert.match(m[0], /preventDefault\(\)/, 'context-lost handler must call preventDefault()');
+    assert.match(m[0], /_ctxLost\s*=\s*true/, 'context-lost handler must set _ctxLost = true');
+});
+
+test('draw() early-returns while the context is lost', () => {
+    assert.match(src, /draw\(bundle\)\s*\{[\s\S]*?if\s*\(_ctxLost\)\s*return;/,
+        'draw() must bail while _ctxLost is set so no GL work runs on a dead context');
+});
+
+test('teardown removes the context-loss listeners', () => {
+    assert.match(src, /removeEventListener\(\s*['"]webglcontextlost['"]/,
+        'teardown must remove the webglcontextlost listener');
+    assert.match(src, /removeEventListener\(\s*['"]webglcontextrestored['"]/,
+        'teardown must remove the webglcontextrestored listener');
+});