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/mirror.js

@@ -1,4 +1,4 @@
-'use strict';
+'use strict';
 /* ══════════════════════════════════════════════════════════════
    MirrorSim v3
    Flat / Concave / Convex  ·  1/f = 1/d + 1/d'  ·  M = -d'/d
@@ -1003,3 +1003,97 @@ class MirrorSim {
     cv.addEventListener('touchend', () => { this._drag=null; });
   }
 }
+
+/* ─── lab UI init ─────────────────────────────────── */
+  var mirrorSim = null;
+
+  function _openMirror() {
+    document.getElementById('sim-topbar-title').textContent = 'Зеркала';
+    _simShow('sim-mirrors');
+    _registerSimState('mirrors', () => mirrorSim?.getParams(), st => mirrorSim?.setParams(st));
+    if (_embedMode) _startStateEmit('mirrors');
+    requestAnimationFrame(() => requestAnimationFrame(() => {
+      if (!mirrorSim) {
+        mirrorSim = new MirrorSim(document.getElementById('mirror-canvas'));
+        mirrorSim.onUpdate = _mirrorUpdateUI;
+        mirrorSim.onAnimate = (d) => {
+          const sl = document.getElementById('sl-mirror-d');
+          const lbl = document.getElementById('mirror-d-val');
+          if (sl) sl.value = Math.round(d);
+          if (lbl) lbl.textContent = Math.round(d);
+        };
+      }
+      mirrorSim.fit();
+      mirrorSim.draw();
+      mirrorSim._emit();
+      if (mirrorSim._showPhotons && !mirrorSim._photonRaf) mirrorSim._startPhotons();
+    }));
+  }
+
+  function mirrorType(type, el) {
+    document.querySelectorAll('.mirror-type-btn').forEach(b => b.classList.remove('active'));
+    if (el) el.classList.add('active');
+    const fRow = document.getElementById('mirror-f-row');
+    if (fRow) fRow.style.display = type === 'flat' ? 'none' : 'flex';
+    if (mirrorSim) mirrorSim.setType(type);
+    const pb = document.getElementById('mirror-play-btn');
+    if (pb) { pb.textContent = '▶ Анимация'; }
+    const sl = document.getElementById('sl-mirror-d');
+    if (sl) sl.disabled = false;
+  }
+
+  function mirrorParam(name, val) {
+    const v = parseFloat(val);
+    const ids = { f: 'mirror-f-val', d: 'mirror-d-val', h: 'mirror-h-val' };
+    const el = document.getElementById(ids[name]);
+    if (el) el.textContent = v;
+    if (mirrorSim) mirrorSim.setParams({ [name]: v });
+  }
+
+  function mirrorPreset(name) {
+    const P = {
+      flat:    { type: 'flat',    f: 120, d: 200, h: 60 },
+      far:     { type: 'concave', f: 100, d: 280, h: 60 },
+      '2f':    { type: 'concave', f: 100, d: 200, h: 60 },
+      between: { type: 'concave', f: 100, d: 140, h: 60 },
+      near:    { type: 'concave', f: 100, d: 60,  h: 60 },
+      convex:  { type: 'convex',  f: 100, d: 200, h: 60 },
+    };
+    const p = P[name]; if (!p) return;
+    document.querySelectorAll('.mirror-type-btn').forEach(b => b.classList.remove('active'));
+    const tb = document.getElementById(`mtype-${p.type}`);
+    if (tb) tb.classList.add('active');
+    const fRow = document.getElementById('mirror-f-row');
+    if (fRow) fRow.style.display = p.type === 'flat' ? 'none' : 'flex';
+    document.getElementById('sl-mirror-f').value = p.f; document.getElementById('mirror-f-val').textContent = p.f;
+    document.getElementById('sl-mirror-d').value = p.d; document.getElementById('mirror-d-val').textContent = p.d;
+    document.getElementById('sl-mirror-h').value = p.h; document.getElementById('mirror-h-val').textContent = p.h;
+    if (mirrorSim) { mirrorSim.setType(p.type); mirrorSim.setParams({ f: p.f, d: p.d, h: p.h }); }
+  }
+
+  function mirrorTogglePlay(btn) {
+    if (!mirrorSim) return;
+    mirrorSim.togglePlay();
+    const playing = mirrorSim._playing;
+    if (btn) btn.textContent = playing ? '⏸ Стоп' : '▶ Анимация';
+    const sl = document.getElementById('sl-mirror-d');
+    if (sl) sl.disabled = playing;
+  }
+
+  function mirrorSetSpeed(val)       { if (mirrorSim) mirrorSim.setAnimSpeed(parseFloat(val)); }
+  function mirrorToggle(name, val)   { if (mirrorSim) mirrorSim.setToggle(name, val); }
+  function mirrorStepNext()          { if (mirrorSim) mirrorSim.stepNext(); }
+  function mirrorStepReset()         { if (mirrorSim) mirrorSim.stepReset(); }
+  function mirrorSetPointMode(val)   { if (mirrorSim) mirrorSim.setPointMode(val); }
+
+  function _mirrorUpdateUI(info) {
+    const v = (id, val) => { const el = document.getElementById(id); if (el) el.textContent = val; };
+    v('mirrorbar-v1', info.f);
+    v('mirrorbar-v5', Math.round(info.d));
+    v('mirrorbar-v2', info.dPrime === Infinity ? '∞' : info.dPrime);
+    v('mirrorbar-v3', info.M === Infinity ? '∞' : info.M);
+    v('mirrorbar-v4', info.imageType);
+  }
+
+  /* ── isoprocesses ── */
+