refactor(h3d-carve-7): extract O-section (lyrics + HUD overlay) → src/overlay.js

Move longestConsecutiveRun, drawChordDiagram, _drawDiagramCached,
drawSectionHud, drawToneHud, drawLyrics out of screen.js IIFE into
plugins/highway_3d/src/overlay.js as export function createOverlay({ diagRenderCache }).

Surprises vs approved contract:
  • longestConsecutiveRun (lines 4338–4352) co-moved — called only by drawChordDiagram
  • DIAG_SIZE_MIN, DIAG_SIZE_MAX, DIAG_CELL_MAX DELETED from screen.js (lines 573–575);
    only users were inside the O-section; moved not copied to avoid drift
  • _DIAG_CACHE_MAX DELETED from screen.js factory scope (line 3256); moved not copied

Beyond-subst rewires (2):
  1. Factory wrapper createOverlay({ diagRenderCache })
  2. _diagRenderCache → diagRenderCache (DI param) in 3 sites in _drawDiagramCached

Base run stated: 253/253 on a993d2b
Post-cut: 262/262 (+9 tests — 8 overlay class-killers + 1 panel-controls stub)

Named mutations verified RED:
  • createOverlay({ diagRenderCache: new Map() }) → test 6 RED (ref-severance)
  • void _DIAG_CACHE_MAX in screen.js         → test 4 RED (bare private)

plugin.json: 3.42.0 → 3.43.0

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

plugins/highway_3d/plugin.json

@@ -1,7 +1,7 @@
 {
   "id": "highway_3d",
   "name": "3D Highway",
-  "version": "3.42.0",
+  "version": "3.43.0",
   "type": "visualization",
   "scriptType": "module",
   "bundled": true,