refactor: distribute lab-init.js into 34 engine files

lab-init.js: 4098 -> 543 lines (infrastructure + THEORY only)

Each sim's _open*() + UI helpers moved to its engine file:
graph.js, projectile.js, collision.js, magnetic.js, triangle.js,
geometry.js, trigcircle.js, gas.js (molphys), coulomb.js, circuit.js,
reactions.js (chemistry), newton.js (dynamics), chemsandbox.js,
celldivision.js, photosynthesis.js, angrybirds.js, quadratic.js,
normaldist.js, graphtransform.js, pendulum.js, equilibrium.js,
thinlens.js, mirror.js, isoprocess.js, titration.js, refraction.js,
probability.js, bohratom.js, electrolysis.js, waves.js,
crystal.js, orbitals.js, stereo.js, hydrostatics.js

All 34 engine files syntax-checked OK.

frontend/js/labs/celldivision.js

@@ -1,4 +1,4 @@
-'use strict';
+'use strict';
 /* ════════════════════════════════════════════════════════════════
    CellDivisionSim v2 — интерактивное деление клетки
    Митоз и мейоз · анимация · частицы · скрабинг · клик
@@ -813,3 +813,80 @@ function _cdRRect(ctx, x, y, w, h, r) {
   ctx.arcTo(x, y, x + w, y, r);
   ctx.closePath();
 }
+
+/* ─── lab UI init ─────────────────────────────────── */
+  function _openCellDivision(mode) {
+    document.getElementById('sim-topbar-title').textContent = 'Деление клетки';
+    _simShow('sim-celldivision');
+    _simShow('ctrl-celldivision');
+    requestAnimationFrame(() => requestAnimationFrame(() => {
+      const canvas = document.getElementById('celldiv-canvas');
+      if (!cellDivSim) {
+        cellDivSim = new CellDivisionSim(canvas);
+        cellDivSim.onUpdate = _cdUpdateUI;
+      }
+      cellDivSim.fit();
+      cellDivSim.setMode(mode || 'mitosis');
+      cellDivSim.start();
+      _cdBuildDots(cellDivSim._phaseIdx);
+      // sync auto button state
+      const autoBtn = document.getElementById('cd-auto-btn');
+      if (autoBtn) { autoBtn.innerHTML = cellDivSim._autoPlay ? '<svg class="ic" viewBox="0 0 24 24"><rect x="6" y="4" width="4" height="16"/><rect x="14" y="4" width="4" height="16"/></svg> Пауза' : '<svg class="ic" viewBox="0 0 24 24"><polygon points="5 3 19 12 5 21 5 3"/></svg> Авто'; }
+      _cdUpdateUI(cellDivSim.info());
+    }));
+  }
+
+  function _cdBuildDots(activeIdx) {
+    const box = document.getElementById('cd-phase-dots');
+    if (!box || !cellDivSim) return;
+    const phases = cellDivSim._phases();
+    box.innerHTML = phases.map((p, i) =>
+      `<div class="cd-phase-dot${i === activeIdx ? ' active' : ''}" onclick="cdJumpPhase(${i})" title="${p.label}"></div>`
+    ).join('');
+  }
+
+  function cdSetMode(mode, btn) {
+    document.querySelectorAll('.cd-mode-btn').forEach(b => b.classList.remove('active'));
+    if (btn) btn.classList.add('active');
+    if (!cellDivSim) return;
+    cellDivSim.setMode(mode);
+    _cdBuildDots(cellDivSim._phaseIdx);
+    _cdUpdateUI(cellDivSim.info());
+  }
+
+  function cdAutoPlay(btn) {
+    if (!cellDivSim) return;
+    cellDivSim.toggleAutoPlay();
+    btn.classList.toggle('active', cellDivSim._autoPlay);
+    btn.innerHTML = cellDivSim._autoPlay ? '<svg class="ic" viewBox="0 0 24 24"><rect x="6" y="4" width="4" height="16"/><rect x="14" y="4" width="4" height="16"/></svg> Пауза' : '<svg class="ic" viewBox="0 0 24 24"><polygon points="5 3 19 12 5 21 5 3"/></svg> Авто';
+  }
+
+  function cdPrevPhase() {
+    if (!cellDivSim) return;
+    cellDivSim.prevPhase();
+    _cdBuildDots(cellDivSim._phaseIdx);
+  }
+
+  function cdNextPhase() {
+    if (!cellDivSim) return;
+    cellDivSim.nextPhase();
+    _cdBuildDots(cellDivSim._phaseIdx);
+  }
+
+  function cdJumpPhase(idx) {
+    if (!cellDivSim) return;
+    cellDivSim.jumpToPhase(idx);
+    _cdBuildDots(idx);
+  }
+
+  function _cdUpdateUI(info) {
+    const v = (id, val) => { const el = document.getElementById(id); if (el) el.textContent = val; };
+    v('cdbar-v1', info.phase || '—');
+    v('cdbar-v2', info.chromN || '—');
+    v('cdbar-v3', info.dna || '—');
+    v('cdbar-v4', (info.index + 1) + ' / ' + info.total);
+    v('cdbar-v5', info.mode === 'mitosis' ? 'Митоз' : 'Мейоз');
+    _cdBuildDots(info.index);
+  }
+
+  /* ── Photosynthesis / Respiration ── */