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>

tests/test_editor_quick_edit_fill_fgbg.py

@@ -0,0 +1,22 @@
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+GALLERY = ROOT / "static/js/galleryEditor.js"
+
+
+def test_fill_fgbg_names_the_colour_in_status():
+    src = GALLERY.read_text(encoding="utf-8")
+    # Edit ▸ Fill with an explicit foreground/background colour and no
+    # selection fills the whole layer and reports the exact colour used.
+    assert "const _fgBgLabel = /\\bbackground\\b/.test(p) ? 'background' : 'foreground';" in src
+    assert "Filled the layer with the ${_fgBgLabel} colour (${color})." in src
+
+
+def test_fill_fgbg_fills_the_whole_layer():
+    src = GALLERY.read_text(encoding="utf-8")
+    idx = src.index("const _fgBgLabel")
+    block = src[idx - 400:idx]
+    assert "selection.selectAll" in block
+    assert "selection.fill" in block
+    assert "selection.deselect" in block