fix(highway_3d): hoist sY before createScoreFx to resolve TDZ

Root cause: const sY was declared 371 lines after createScoreFx({..., sY})
inside createFactory(). The shorthand {sY} reads the binding immediately
(not a closure), so every factory call threw ReferenceError: Cannot access
'sY' before initialization. highway.js caught it, reverted to 2D, emitted
viz:reverted. THREE.js was never requested.

Fix: hoist sY declaration to just before createScoreFx. Also hoist
_invertedCached, nStr, curX, and highwayCanvas above their first lexical
reference (all were closure false positives, but hoisting makes the code
unambiguously safe and keeps the new ESLint gate clean with 0 errors).
Hoist _bcPanel in bc-panel.js for the same reason.

Regression gate: eslint no-use-before-define (variables:true, functions:false)
scoped over plugins/highway_3d/ (screen.js + src/). Statically catches any
const/let used before its declaration in the factory — the whole class, not
just this pair. RED at broken tip (sY flagged): GREEN after fix.
Pre-existing violations surfaced (all closure false positives, none true TDZ
runtime bugs): highwayCanvas in _v3TopRightChromeBottom body, _invertedCached
and nStr in sY arrow body and DI getters, curX in getCurX DI getter, _bcPanel
in bc-panel.js function bodies — all resolved by hoisting; no silenced errors.

Bump plugin.json 3.53.0→3.54.0 (viz factory change per standing rule).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014uZ169yfoFYArXz962g7KW

tests/js/highway_3d_score_fx.test.js

@@ -462,3 +462,47 @@ test('createScoreFx({...}) wiring has correct naming correspondence (no param sw
 
     assert.deepEqual(violations, [], 'createScoreFx wiring violations found');
 });
+
+// ── TDZ regression guard (fix/h3d-viz-init-fallback) ────────────────────────
+// Input that FAILS at broken tip: calling window.feedBackViz_highway_3d()
+// (i.e. createFactory()) throws ReferenceError: Cannot access 'sY' before
+// initialization — const sY was declared 371 lines AFTER createScoreFx({...,
+// sY}), putting sY in the temporal dead zone on every factory invocation.
+// Result: viz picker fell back to 2D immediately; THREE.js never requested.
+//
+// Guard: ESLint no-use-before-define (variables:true, functions:false) scoped
+// over screen.js and src/ — statically flags ANY const/let used before its
+// declaration in the factory, catching the entire class not just this pair.
+// At the broken tip this rule errors on sY; after the fix it is clean.
+// Prefer this semantic gate over source-scan byte-offset comparisons, which
+// miss TDZ bugs invisible to regex (this was the FOURTH such break).
+test('no-use-before-define gate is clean on highway_3d screen.js and src/ (fix/h3d-viz-init-fallback)', () => {
+    const { execSync } = require('node:child_process');
+    const repoRoot = path.join(__dirname, '..', '..');
+    let stdout;
+    try {
+        stdout = execSync(
+            'npx --yes eslint@9.39.4 --format json plugins/highway_3d/screen.js plugins/highway_3d/src/',
+            { cwd: repoRoot, encoding: 'utf8' },
+        );
+    } catch (err) {
+        // eslint exits non-zero when errors exist; output is still on stdout.
+        stdout = err.stdout || '';
+    }
+    const results = JSON.parse(stdout);
+    const tdzErrors = [];
+    for (const file of results) {
+        for (const msg of file.messages) {
+            if (msg.ruleId === 'no-use-before-define' && msg.severity === 2) {
+                tdzErrors.push(`${path.relative(repoRoot, file.filePath)}:${msg.line} — ${msg.message}`);
+            }
+        }
+    }
+    assert.deepEqual(
+        tdzErrors,
+        [],
+        'no-use-before-define errors found in highway_3d — a const/let is used before its ' +
+        'declaration in the factory (real TDZ risk). At the broken tip, sY was used in ' +
+        'createScoreFx({..., sY}) 371 lines before its declaration.\n' + tdzErrors.join('\n'),
+    );
+});