feat(grid): add image preview viewer

packages/app-tests/imagePreviewViewer.test.ts

@@ -0,0 +1,26 @@
+import { strict as assert } from "node:assert";
+import test from "node:test";
+import {
+  clampImagePreviewScale,
+  imagePreviewTransform,
+  nextImagePreviewScale,
+} from "../../apps/desktop/src/lib/imagePreviewViewer.ts";
+
+test("clamps image preview zoom to usable bounds", () => {
+  assert.equal(clampImagePreviewScale(0.1), 0.2);
+  assert.equal(clampImagePreviewScale(1.25), 1.25);
+  assert.equal(clampImagePreviewScale(12), 8);
+});
+
+test("zooms in fixed steps from wheel direction", () => {
+  assert.equal(nextImagePreviewScale(1, "in"), 1.2);
+  assert.equal(nextImagePreviewScale(1, "out"), 0.8);
+  assert.equal(nextImagePreviewScale(7.95, "in"), 8);
+});
+
+test("builds a stable CSS transform for image previews", () => {
+  assert.equal(
+    imagePreviewTransform({ scale: 1.5, rotation: 90, offsetX: 12, offsetY: -8 }),
+    "translate(12px, -8px) rotate(90deg) scale(1.5)",
+  );
+});