debug: add gesture diagnostic logs gated behind globalThis.RUBIK_DEBUG

Temporary instrumentation to diagnose residual edge-rotation reversal
that survives the face-anchor fix. Logs hit context, gesture math, and
the committed move spec so we can trace any remaining sign mismatch.

Disabled by default — set `RUBIK_DEBUG = true` in the browser console to
enable. Will be removed once the residual bug is localized.

src/lib/controls/gesture-math.js

@@ -65,6 +65,21 @@ export function chooseRotationAxis({ hitFaceAxis, hitWorldPos, dx, dy, projectFn
     const motionScreen = projectFn(hitWorldPos.clone().add(motionWorld)).sub(screenOrigin);
     const signMul = motionScreen.dot(drag) >= 0 ? 1 : -1;
 
+    if (typeof globalThis !== 'undefined' && globalThis.RUBIK_DEBUG) {
+        console.log('[GESTURE]', {
+            hitFaceAxis,
+            hitWorldPos: [hitWorldPos.x.toFixed(3), hitWorldPos.y.toFixed(3), hitWorldPos.z.toFixed(3)],
+            drag: [dx, dy],
+            projs: projs.map((p) => p.toFixed(3)),
+            dragAxis,
+            rotAxis,
+            faceAnchor: [faceAnchor.x, faceAnchor.y, faceAnchor.z],
+            motionWorld: [motionWorld.x.toFixed(3), motionWorld.y.toFixed(3), motionWorld.z.toFixed(3)],
+            motionScreen: [motionScreen.x.toFixed(3), motionScreen.y.toFixed(3)],
+            signMul
+        });
+    }
+
     return {
         rotAxis,
         dragAxis,

src/lib/controls/pointer-gesture.js

@@ -80,6 +80,15 @@ export function setupPointerGesture({ canvas, camera, controls, parentGroup, mes
             return;
         }
         const hitWorldPos = hitMesh.getWorldPosition(new Vector3());
+        if (typeof globalThis !== 'undefined' && globalThis.RUBIK_DEBUG) {
+            const cubie = hitMesh.userData.cubie;
+            console.log('[HIT]', {
+                hitFaceAxis,
+                hitWorldPos: [hitWorldPos.x.toFixed(3), hitWorldPos.y.toFixed(3), hitWorldPos.z.toFixed(3)],
+                cubieHome: cubie.home,
+                cubiePosition: cubie.position
+            });
+        }
         const decision = chooseRotationAxis({
             hitFaceAxis,
             hitWorldPos,
@@ -143,6 +152,9 @@ export function setupPointerGesture({ canvas, camera, controls, parentGroup, mes
         const sign = turns > 0 ? 1 : -1;
         const count = Math.abs(turns) === 2 ? 2 : 1;
         const spec = { axis: pivotAxis, layer: layerIndex, sign, count, name: '' };
+        if (typeof globalThis !== 'undefined' && globalThis.RUBIK_DEBUG) {
+            console.log('[COMMIT]', { curAngle: curAngle.toFixed(3), turns, spec, name: specToName(spec) });
+        }
         snapAndAnimate({
             parentGroup, pivot, meshes, cubies, spec,
             fromAngle: curAngle, toAngle: targetAngle, durationMs: 120