Openings get descriptions: zone is the keyword, this is the sentence

Eric's ask. Free text on any opening ("tall bookcase by the window —
kids reach the bottom rows"), edited in the opening settings sheet,
shown under the sheet's title, and surfaced as the cell's hover title
on the wall diagram. Stored in furniture.json like everything else.

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

tests/test_shelves.py

@@ -800,3 +800,23 @@ def test_reunification_outranks_tightest_fit_and_full_shelves_stop_lying(tmp_pat
     exp = next(g for g in state["unshelved"] if g["name"].endswith("Tower"))
     first = exp["suggestions"][0]
     assert first["id"] == ids["A1"] and first["reunites"] is True
+
+
+def test_opening_descriptions_round_trip(tmp_path):
+    web, cfg = _web(tmp_path, {})
+    web.post("/api/furniture/add-unit", json={"name": "Den"})
+    web.post("/api/furniture/add-openings", json={"unit": "Den", "label": "top"})
+    oid = web.get("/api/shelves").json()["units"][0]["openings"][0]["id"]
+    web.post(
+        "/api/furniture/edit-opening",
+        json={
+            "id": oid,
+            "description": "tall bookcase by the window",
+        },
+    )
+    opening = web.get("/api/shelves").json()["units"][0]["openings"][0]
+    assert opening["description"] == "tall bookcase by the window"
+    import json as _json
+
+    saved = _json.loads(cfg.furniture_path.read_text())["units"][0]["openings"][0]
+    assert saved["description"] == "tall bookcase by the window"