feat(render): wheel + trackpad-pinch zoom in every mode

Reusable zoom control (zoomControl.js): RK.attachZoom(host) adds wheel/pinch zoom
to a render host; RK.applyZoom(host) scales whatever canvas is mounted (2D or
WebGL) via CSS transform (pixelated so pixel art stays crisp), re-applied on mode
switch. Trackpad pinch = ctrl+wheel, handled the same way; double-click resets.
Wired into the tavern stage, so it works across Tiled/ASCII/Fancy/Iso/3D. Client-only.

html/js/render/zoomControl.js

@@ -0,0 +1,40 @@
+(function (root) {
+    'use strict';
+    var RK = root.RK = root.RK || {};
+
+    var MIN = 0.4, MAX = 4.0;
+
+    // Apply the host's current zoom to whatever canvas is mounted in it (2D or WebGL). Re-callable
+    // after a renderer/mode switch so the new canvas inherits the zoom.
+    RK.applyZoom = function (host) {
+        if (!host) return;
+        var z = host._rkZoom || 1;
+        var c = host.querySelector('canvas');
+        if (!c) return;
+        c.style.transformOrigin = 'center center';
+        c.style.transform = z === 1 ? '' : 'scale(' + z + ')';
+        c.style.imageRendering = 'pixelated'; // keep pixel art crisp when zoomed
+    };
+
+    // Wheel + trackpad-pinch zoom on a render host, shared by every mode. Trackpad pinch arrives as
+    // a wheel event with ctrlKey set; a normal wheel over the canvas zooms instead of scrolling.
+    RK.attachZoom = function (host) {
+        if (!host || host._rkZoomAttached) return;
+        host._rkZoomAttached = true;
+        host._rkZoom = host._rkZoom || 1;
+        host.style.overflow = 'hidden';
+        host.title = 'Scroll / pinch to zoom · double-click to reset';
+
+        host.addEventListener('wheel', function (e) {
+            e.preventDefault();
+            var factor = Math.exp(-e.deltaY * 0.0015);      // smooth, direction-correct
+            host._rkZoom = Math.max(MIN, Math.min(MAX, (host._rkZoom || 1) * factor));
+            RK.applyZoom(host);
+        }, { passive: false });
+
+        host.addEventListener('dblclick', function () {
+            host._rkZoom = 1;
+            RK.applyZoom(host);
+        });
+    };
+})(window);

html/tavern.html

@@ -14,6 +14,7 @@
     <script src="js/render/atlas.js"></script>
     <script src="js/render/charSprites.js"></script>
     <script src="js/render/catSprites.js"></script>
+    <script src="js/render/zoomControl.js"></script>
     <script src="js/render/assetPacks.js"></script>
     <script src="js/render/avatarVisuals.js"></script>
     <script src="js/render/designedRoom.js"></script>
@@ -216,6 +217,7 @@
                 if (currentMode !== mode) { r.destroy(); return; } // switched again while loading
                 currentRenderer = r;
                 draw();
+                if (RK.attachZoom) { RK.attachZoom(stageEl); RK.applyZoom(stageEl); } // wheel/pinch zoom, all modes
                 var active = r.name || mode;
                 setStatus(active === mode
                     ? 'Render mode: ' + active