h3d-carve-10: extract K-section (score FX) into src/score-fx.js

VERBATIM-MOVE of the score-FX block from screen.js into a new
createScoreFx() factory. 7 DI-rewires only (getNdFrameNowMs,
getCam, getProbe, getNStr, getCurX, getHighwayCanvas × closure,
sY shorthand). No logic changes.

Four regions in screen.js replaced with factory callsites:
- State block (old lines 3619–3720): createScoreFx({…}) destructure
- drawScoreFx body (old 12564–12672): tombstone comment
- Init block (old 5839–5862): fxInit() callsite
- Teardown lines (old 12796/12814–12820): fxTeardown() callsite;
  _fxOnSkin removal moved into fxTeardown(), feedBack block
  restructured to contain only non-K-section listeners.

Tests (highway_3d_score_fx.test.js, 37 new, all green):
- Gut-audit: all 4 exports + _fxHandle + _fxSpawnPop paths
- Class-killers: fxTeardown listener removal, _fxGen increment
- Verbatim-declaration: no re-entry guard in fxInit (per dispatch)
- Wiring-correspondence guard: createScoreFx({…}) naming (cut-9
  pattern, empty PINNED_RENAMES)

Pre-existing failures: #46 (legacy analyser), #628 (nut-labels) —
both pre-date this cut, confirmed against 4a45ed8 baseline.

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": "3.45.0",
+  "version": "3.46.0",
   "type": "visualization",
   "scriptType": "module",
   "bundled": true,