feat: consolidate shared UI and harden browser authority for release

webui/tests/data-grid-sizing.test.ts

@@ -1,4 +1,5 @@
 import {
+  dataGridActionTrackMinimum,
   dataGridLayoutSignature,
   dataGridWidthsForLayout,
   distributeDataGridResizeAmount,
@@ -408,7 +409,14 @@ assertEqual(
   "free and cover layouts keep independent user overrides"
 );
 assertEqual(
-  originalSignature.startsWith("v2::"),
+  originalSignature.startsWith("v3::"),
   true,
   "the responsive persistence contract invalidates legacy hard-width snapshots"
 );
+
+assertEqual(dataGridActionTrackMinimum({ id: "actions", width: 72 }, 182, 800), 182, "four action slots override a clipped preferred width");
+assertEqual(dataGridActionTrackMinimum({ id: "actions" }, 182, 280), 140, "narrow action groups leave room to read row data and wrap");
+assertEqual(dataGridActionTrackMinimum({ id: "actions", minWidth: 160 }, 182, 280), 160, "declared action hard minima remain authoritative");
+assertEqual(dataGridActionTrackMinimum({ id: "actions" }, Number.NaN, 400), 72, "invalid content measurements cannot poison tracks");
+assertEqual(dataGridLayoutSignature([{ id: "first", filterable: true }], "container", "cover")
+  === dataGridLayoutSignature([{ id: "first" }], "container", "cover"), false, "changed header controls invalidate obsolete persisted minima");