No placebo buttons: accept-overhang only offered when it would help

Eric clicked accept-overhang on two boxes in a Kallax cube and got an
"overhang ✓" pill with no lane behind it. The cube's flat pile claims
11.7 of 13.25 inches of width, leaving 1.55 inches of standing lane —
acknowledging waives depth and height, never width, so nothing changed.
That opening is overfull, not overhung, and the button was a placebo.

The sheet now probes before offering: a laneless resident gets the
accept button only when acknowledging would actually land it a lane;
otherwise it's marked "no room" with the honest tooltip. Acknowledged
boxes that DID land show "▮ standing, proud" (their lane isn't
flippable — proud of the shelf is the whole point), plus the
retractable "overhang ✓". Verified against the live wall: the three
Etherfields monoliths on the tower's big row read standing-proud, the
squeezed cube residents read no-room, zero page errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jXZFSTZQKzAC8fqpWSz9g

tests/test_shelves.py

@@ -1095,3 +1095,64 @@ def test_import_acknowledge_column(tmp_path):
         "lane": "standing",
         "acknowledged": True,
     }
+
+
+def test_ackable_only_when_it_helps(tmp_path):
+    """The accept-overhang button is offered only when acknowledging
+    would actually give the box a lane. A depth-blocked box on a shallow
+    shelf is ackable; a box squeezed out of a width-starved opening is
+    overfull, not overhung — no placebo button."""
+    web, cfg = _web(
+        tmp_path,
+        {
+            "1": _entry("Wide Flat", 13.0, 13.0, 12.0),
+            "2": _entry("Squeezed Out", 10.0, 10.0, 3.0),
+            "3": _entry("Etherfields", 11.8, 11.8, 2.9),
+        },
+    )
+    save_furniture(
+        cfg,
+        [
+            {
+                "name": "Mix",
+                "openings": [
+                    {
+                        "id": "cube",
+                        "label": "A1",
+                        "zone": "",
+                        "width_in": 13.25,
+                        "height_in": 13.25,
+                        "depth_in": 15.4,
+                    },
+                    {
+                        "id": "tower",
+                        "label": "B1",
+                        "zone": "",
+                        "width_in": 23.25,
+                        "height_in": 19.0,
+                        "depth_in": 9.5,
+                    },
+                ],
+            }
+        ],
+    )
+    save_locations(
+        cfg,
+        {
+            "1": {"opening_id": "cube", "note": ""},
+            "2": {"opening_id": "cube", "note": ""},
+            "3": {"opening_id": "tower", "note": ""},
+        },
+    )
+    units = web.get("/api/shelves").json()["units"]
+    by_label = {o["label"]: o for o in units[0]["openings"]}
+    cube = {g["name"]: g for g in by_label["A1"]["resident_games"]}
+    # the wide flat box claims 13.0" of a 13.25" opening: 0.25" of
+    # standing lane left — acknowledging Squeezed Out changes nothing
+    assert cube["Squeezed Out"]["laneless"] is True
+    assert cube["Squeezed Out"]["ackable"] is False
+    tower = {g["name"]: g for g in by_label["B1"]["resident_games"]}
+    # the classic overhang: no lane takes 11.8" of depth on a 9.5"
+    # shelf, but standing proud works — offer the button
+    assert tower["Etherfields"]["laneless"] is True
+    assert tower["Etherfields"]["ackable"] is True