feat(photo-editor): Ajax Image Editor client (Photoshop-parity tools)

Photoshop-parity editor client: layers, selection/masking, brushes,
smart filters, LUT import, Quick Edit, mobile gestures, workspaces,
batch operations, and the service-worker versioning (v978->v1006).

Source: vendor/photocraft (ad1cff44) photo-editor client files, merged
onto upstream/dev (a8c147b2). Conflict resolution documented in
pr_work/A_conflicts.md; editor files taken from vendor/photocraft
(upstream's editor is an earlier snapshot of the same feature).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

static/js/editor/mask-ops.js

@@ -0,0 +1,62 @@
+// Small, dependency-light mask helpers used by the editor-control mask
+// operations (add-mask-from-selection, apply/invert/feather) and per-layer
+// vision ops (get bounds). Pure data helpers are exported so they can be unit
+// tested in Node without a real canvas.
+
+// Bounding box of non-transparent pixels. `data` is RGBA (Uint8ClampedArray or
+// plain array), row-major, length width*height*4. Returns {x,y,w,h} or null.
+export function alphaBounds(data, width, height, threshold = 8) {
+  if (!data || !(width > 0) || !(height > 0)) return null;
+  let minX = width, minY = height, maxX = -1, maxY = -1;
+  for (let y = 0; y < height; y++) {
+    const row = y * width;
+    for (let x = 0; x < width; x++) {
+      const a = data[(row + x) * 4 + 3];
+      if (a > threshold) {
+        if (x < minX) minX = x;
+        if (x > maxX) maxX = x;
+        if (y < minY) minY = y;
+        if (y > maxY) maxY = y;
+      }
+    }
+  }
+  if (maxX < 0) return null;
+  return { x: minX, y: minY, w: maxX - minX + 1, h: maxY - minY + 1 };
+}
+
+// Invert a mask stored as white RGB + alpha (selected = alpha 255). Returns a
+// NEW array; the source is not mutated.
+export function invertMaskData(data) {
+  const out = new Uint8ClampedArray(data.length);
+  for (let i = 0; i < data.length; i += 4) {
+    out[i] = 255;
+    out[i + 1] = 255;
+    out[i + 2] = 255;
+    out[i + 3] = 255 - data[i + 3];
+  }
+  return out;
+}
+
+// Blur (feather) a mask canvas into a fresh canvas. `createCanvas(w,h)` must
+// return a canvas-like object with getContext('2d'). Returns the new canvas.
+export function featherMaskCanvas(createCanvas, srcCanvas, radius) {
+  const w = srcCanvas.width, h = srcCanvas.height;
+  const out = createCanvas(w, h);
+  const ctx = out.getContext('2d');
+  const r = Math.max(0, Number(radius) || 0);
+  if (r > 0 && 'filter' in ctx) ctx.filter = `blur(${r}px)`;
+  ctx.drawImage(srcCanvas, 0, 0);
+  if (r > 0 && 'filter' in ctx) ctx.filter = 'none';
+  return out;
+}
+
+// Bake a mask into a layer by multiplying the layer alpha (destination-in).
+export function bakeMaskIntoLayer(layerCtx, maskCanvas, offsetX = 0, offsetY = 0) {
+  layerCtx.save();
+  layerCtx.globalCompositeOperation = 'destination-in';
+  layerCtx.drawImage(maskCanvas, offsetX, offsetY);
+  layerCtx.restore();
+  return true;
+}
+
+export default { alphaBounds, invertMaskData, featherMaskCanvas, bakeMaskIntoLayer };