fix(explore): align the expand chevron to the top band

apps/escurel-explore/lib/crm/crm_workspace.dart

@@ -190,11 +190,20 @@ class _CollapsibleRegion extends StatelessWidget {
             message: 'Expand',
             child: InkWell(
               onTap: onToggle,
-              child: Center(
-                child: Icon(
-                  edge == _Edge.right ? Icons.chevron_right : Icons.chevron_left,
-                  size: 16,
-                  color: kOnSurfaceVariant,
+              // Whole rail stays tappable, but the chevron sits in the
+              // same top 28px band as the collapse chevron (consistent
+              // placement) rather than floating at the vertical centre.
+              child: Align(
+                alignment: Alignment.topCenter,
+                child: SizedBox(
+                  height: 28,
+                  child: Center(
+                    child: Icon(
+                      edge == _Edge.right ? Icons.chevron_right : Icons.chevron_left,
+                      size: 16,
+                      color: kOnSurfaceVariant,
+                    ),
+                  ),
                 ),
               ),
             ),

apps/escurel-explore/test/crm/both_panes_collapse_test.dart

@@ -71,11 +71,11 @@ void main() {
     await tester.pumpAndSettle();
     expect(find.bySemanticsLabel('event-pane'), findsNothing);
 
-    // Tap near the TOP of the collapsed rail — far from the vertically
-    // centered chevron icon. Before the full-rail hit target, only the
-    // ~16px icon responded, so a real click that missed it did nothing.
+    // Tap low in the collapsed rail — well away from the chevron icon
+    // (which sits in the top band). Only a full-rail hit target responds
+    // here; the old centered-icon target would have ignored this click.
     final rail = tester.getRect(find.bySemanticsLabel('region-events'));
-    await tester.tapAt(Offset(rail.center.dx, rail.top + 24));
+    await tester.tapAt(Offset(rail.center.dx, rail.top + rail.height * 0.75));
     await tester.pumpAndSettle();
     expect(find.bySemanticsLabel('event-pane'), findsOneWidget,
         reason: 'tapping the rail (off the icon) must still expand it');