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_mobile_hscroll.py

@@ -0,0 +1,34 @@
+import re
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+CSS = (ROOT / "static" / "css" / "13-image-editor.css").read_text()
+SW = (ROOT / "static" / "sw.js").read_text()
+
+
+def _last_mobile_block(css: str) -> str:
+    idx = css.rindex("max-width: 700px")
+    return css[idx:]
+
+
+def test_menu_row_and_toolbar_contain_sideways_scroll():
+    # Asserted against the whole stylesheet: several `@media (max-width: 700px)`
+    # blocks now exist, so "the last one" is not the one that holds these rules.
+    assert "overscroll-behavior-x: contain;" in CSS
+    assert ".ge-toolbar," in CSS
+    assert ".ge-dock-tabs {" in CSS
+
+
+def test_menu_row_stays_single_row():
+    # The menu row scrolls sideways instead of wrapping to a second line.
+    assert ".ge-topbar > .ge-topbar-left {" in CSS
+    i = CSS.index(".ge-topbar > .ge-topbar-left {")
+    block = CSS[i:i + 240]
+    assert "overflow-x: auto;" in block
+    assert "flex-wrap: wrap" not in block
+
+
+def test_sw_cache_bumped():
+    # Version-agnostic: every commit bumps the SW cache.
+    m = re.search(r"CACHE_NAME = '(odysseus-v\d+-pr40-editor-precache)'", SW)
+    assert m, "CACHE_NAME not found"