refactor(highway): lift 79 per-instance closure vars into hwState (R3c H lift) (#849)

* refactor(highway): lift 79 per-instance closure vars into `hwState` (R3c H lift)

Collapses createHighway()'s 79 mutable closure `let`s into one per-instance
`hwState` object. Scope-resolved rewrite via acorn + eslint-scope: 1059 edits
(1057 references + 79 defs - the deleted `let canvas, ctx, ws`), with the four
names shadowed in inner scopes (chartTime/ctx/notes/chordTemplates) resolved
correctly so only closure-bound refs move. Enables the later module split:
extracted renderer/ws modules close over `hwState` as a factory arg, so
multi-panel plugins (highway_3d, note_detect, splitscreen) don't share one
highway's state.

Container is `hwState`, NOT `H` — `H` is already canvas height (70 uses). The
frame-time gate caught that collision instantly (0 draws, `H._drawHooks is not
iterable` in the shared draw-hook path).

PERF (the whole risk): identical to the pre-lift baseline. Draw p50 2.1-2.2 ms,
p95 2.7-3.0 ms (pre-lift 2.7-3.2), measured on the Arcturus feedpak, headless.
Each closure-slot read became a `hwState.<slot>` monomorphic property load; the
hot loop pays nothing. On-device: Byron confirmed the 2D highway plays smoothly.

Tests: the ~30 highway JS suites brace-extract functions/patterns from the
source; their state references + the monotonic-clock vm sandbox now use
`hwState.<slot>` (the const _CHART_MAX_INTERP_MS etc. stay top-level, not
lifted). node --test: 1030/1030 green. Two self-inflicted over-replacements
caught and reverted (`_lefty` is a prefix of the 3D-local `_leftyCached`;
`STRING_COLORS` a suffix of `DEFAULT_STRING_COLORS`) — substring replaces on the
brace-extract regexes need word care.

Transformer saved at ~/.local/share/feedback-editor/highway-h-lift.mjs.

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

* test(highway): pin the setNoteStateProvider assertion to hwState._noteStateProvider (CodeRabbit)

The [^}]* form matched an unqualified _noteStateProvider =, so a regression to
closure-level state could still pass. Require the hwState-qualified assignment.

---------

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

tests/js/highway_adaptive_scale.test.js

@@ -29,7 +29,7 @@ function extractBlock(src, signature) {
 
 test('highway declares adaptive-scale state with a floor', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
-    assert.match(src, /let\s+_autoScale\s*=\s*1/, 'missing _autoScale multiplier');
+    assert.match(src, /hwState\._autoScale\s*=\s*1/, 'missing _autoScale multiplier');
     assert.match(src, /const\s+_AUTO_SCALE_MIN\s*=\s*0?\.25/, 'missing _AUTO_SCALE_MIN floor (0.25)');
     assert.match(src, /const\s+_DRAW_BUDGET_HI_MS\s*=\s*\d+/, 'missing high draw budget');
     assert.match(src, /const\s+_DRAW_BUDGET_LO_MS\s*=\s*\d+/, 'missing low draw budget');
@@ -49,18 +49,18 @@ test('_effectiveRenderScale clamps user ceiling * auto factor to [MIN, 1]', () =
 test('min render scale floor is user-configurable + exposed on the api (#654)', () => {
     const src = fs.readFileSync(highwayJs, 'utf8');
     // Hard floor constant kept; configurable floor read from localStorage.
-    assert.match(src, /let\s+_autoScaleMin\s*=/, 'missing configurable _autoScaleMin');
+    assert.match(src, /hwState\._autoScaleMin\s*=/, 'missing configurable _autoScaleMin');
     assert.match(src, /localStorage\.getItem\('highwayMinRenderScale'\)/,
         'configurable floor must load from localStorage.highwayMinRenderScale');
     assert.match(src, /setMinRenderScale\(/, 'api.setMinRenderScale missing');
-    assert.match(src, /getMinRenderScale\(\)\s*\{\s*return\s+_autoScaleMin/, 'api.getMinRenderScale missing');
+    assert.match(src, /getMinRenderScale\(\)\s*\{\s*return\s+hwState\._autoScaleMin/, 'api.getMinRenderScale missing');
     // Floor is clamped to the user ceiling so it can never exceed the manual cap.
     const eff = extractBlock(src, 'function _effectiveRenderScale()');
-    assert.match(eff, /Math\.min\(\s*_autoScaleMin\s*,\s*user\s*\)/,
+    assert.match(eff, /Math\.min\(\s*hwState\._autoScaleMin\s*,\s*user\s*\)/,
         'effective scale must clamp the floor to the user ceiling');
     // _adaptRenderScale must cap the lo bound at 1 so _autoScale stays in [_,1].
     const adapt = extractBlock(src, 'function _adaptRenderScale(');
-    assert.match(adapt, /Math\.min\(\s*1\s*,\s*_autoScaleMin\s*\/\s*_renderScale\s*\)/,
+    assert.match(adapt, /Math\.min\(\s*1\s*,\s*hwState\._autoScaleMin\s*\/\s*hwState\._renderScale\s*\)/,
         'lo bound must be capped at 1 to keep _autoScale a [0,1] multiplier');
 });