fix(labs): SVG markup rendered as text in 6 simulations

Hardcoded inline <svg class="ic"> markers used as arrow replacements

(left over from emoji removal) were displayed as raw HTML text where

the consumer used textContent or canvas fillText:

- chemsandbox: csbar-v5 (Продукты cell) used textContent → SVG visible.

  Switched to innerHTML for consistency with eq/ionNet cells.

  Quiz question (qEl.textContent) and answer also receiving SVG —

  cleaned via _csClean at source.

- reactions: modeTxt drawn via canvas fillText — replaced SVG with →.

- ionexchange: REACTIONS data + canvas labels — bulk SVG → Unicode arrows.

- newton: action button labels used textContent → switched to innerHTML;

  canvas arrow labels: SVG → Unicode →/↓.

- collision: 'KE сохранена' canvas label — SVG checkmark → ✓.

- projectile: canvas badges + textContent wind label — SVG → Unicode ←/→/↩.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/js/labs/collision.js

@@ -709,7 +709,7 @@ class CollisionSim {
         ctx.fillText(label, ix, iy);
       } else if (lossPct === 0 && keBefore > 0.1) {
         const ix = this._impactPt.x, iy = this._impactPt.y - 42;
-        const label = 'KE сохранена <svg class="ic" viewBox="0 0 24 24"><polyline points="20 6 9 17 4 12"/></svg>';
+        const label = 'KE сохранена ✓';
         ctx.font = 'bold 10px Manrope';
         const tw = ctx.measureText(label).width;
         ctx.fillStyle = 'rgba(123,245,164,.15)';