fix(ui): return Escape focus to the rail item and read rail direction from the panel

A desktop side panel hides once collapsed, so Escape hands focus to its visible rail item instead of the hidden disclosure. Rail selection reads the panel's collapsed class rather than the store, which follows it a microtask late.

src/panelEscape.test.mjs

@@ -42,7 +42,7 @@ function panelFixture({ id = 'data-panel', nested = false, nestedCollapsed = fal
     disclosure.closest = () => panel;
   }
   const document = { getElementById: (candidate) => candidate === id ? panel : null };
-  const manager = new Function('document', 'collapsePanelOnEscape', `return {${method('_collapsePanelOnEscape', '_initCommandDockPins')}};`)(document, collapsePanelOnEscape);
+  const manager = new Function('document', 'getComputedStyle', 'collapsePanelOnEscape', `return {${method('_collapsePanelOnEscape', '_initCommandDockPins')}};`)(document, (el) => ({ visibility: el.visibility ?? 'visible' }), collapsePanelOnEscape);
   manager.setPanelCollapsed = (candidate, value, options) => {
     assert.equal(candidate, id);
     assert.equal(value, true);
@@ -55,7 +55,7 @@ function panelFixture({ id = 'data-panel', nested = false, nestedCollapsed = fal
     stopPropagation() { this.propagationStopped = true; },
   };
   return {
-    manager, panel, inner, target, event,
+    manager, panel, inner, target, event, document,
     collapsed: () => collapsed,
     focused: () => focused,
     blurred: () => blurred,
@@ -71,6 +71,41 @@ test('Escape collapses an expanded panel and returns focus to its disclosure', (
   assert.equal(fixture.event.propagationStopped, true);
 });
 
+test('Escape hands focus to the rail item when collapsing hides the panel', () => {
+  const fixture = panelFixture();
+  let railFocused = false;
+  const railItem = {
+    disabled: false,
+    getClientRects: () => [{}],
+    focus: () => { railFocused = true; },
+  };
+  fixture.panel.getClientRects = () => (fixture.collapsed() ? [] : [{}]);
+  fixture.document.querySelector = (selector) => {
+    assert.equal(selector, '.ui-rail [data-rail-item="data-panel"]');
+    return railItem;
+  };
+  assert.equal(fixture.manager._collapsePanelOnEscape(fixture.event, 'data-panel'), true);
+  assert.equal(fixture.collapsed(), true);
+  assert.equal(railFocused, true);
+  assert.equal(fixture.focused(), false, 'not the hidden disclosure');
+});
+
+test('Escape keeps the disclosure path when the rail is hidden', () => {
+  const fixture = panelFixture();
+  let railFocused = false;
+  const railItem = {
+    disabled: false,
+    visibility: 'hidden',
+    getClientRects: () => [{}],
+    focus: () => { railFocused = true; },
+  };
+  fixture.panel.getClientRects = () => (fixture.collapsed() ? [] : [{}]);
+  fixture.document.querySelector = () => railItem;
+  assert.equal(fixture.manager._collapsePanelOnEscape(fixture.event, 'data-panel'), true);
+  assert.equal(railFocused, false);
+  assert.equal(fixture.focused(), true);
+});
+
 test('Escape on an expanded panel disclosure closes it without retaining focus', () => {
   const fixture = panelFixture({ onDisclosure: true });
   assert.equal(fixture.manager._collapsePanelOnEscape(fixture.event, 'data-panel'), true);

src/ui/panelChrome.js

@@ -163,6 +163,22 @@ export class PanelChrome {
         this._locationSearch.value = '';
         this._locationSearch.blur();
       },
+      // A desktop side panel hides entirely once collapsed; its rail item
+      // takes the focus its own disclosure can no longer hold.
+      returnFocusTo: () => {
+        const panel = document.getElementById(panelId);
+        if (!panel?.getClientRects || panel.getClientRects().length > 0)
+          return null;
+        const item = document.querySelector?.(
+          `.ui-rail [data-rail-item="${panelId}"]`,
+        );
+        return item &&
+          !item.disabled &&
+          item.getClientRects().length > 0 &&
+          getComputedStyle(item).visibility === 'visible'
+          ? item
+          : null;
+      },
     });
   }
 

src/ui/panelDisclosure.js

@@ -39,10 +39,14 @@ export function bindPanelDisclosure({
   return { destroy: () => scope.destroy() };
 }
 
-/** Close the nearest expanded panel and return focus to its disclosure. */
+/**
+ * Close the nearest expanded panel and return focus to its disclosure, or to
+ * `returnFocusTo()` when that names a control (a rail item standing in for a
+ * panel that collapsing hid).
+ */
 export function collapsePanelOnEscape(
   event,
-  { panel, onChange, beforeCollapse },
+  { panel, onChange, beforeCollapse, returnFocusTo },
 ) {
   if (event.key !== 'Escape' || event.defaultPrevented) return false;
   if (
@@ -59,6 +63,11 @@ export function collapsePanelOnEscape(
   event.stopPropagation();
   beforeCollapse?.();
   onChange(true, { explicit: true });
+  const stand = returnFocusTo?.();
+  if (stand) {
+    stand.focus?.({ preventScroll: true });
+    return true;
+  }
   const disclosure =
     panel.querySelector(`[data-dock-toggle-target="${panel.id}"]`) ||
     panel.querySelector(`[data-collapse-target="${panel.id}"]`);

src/ui/panelNavigation.js

@@ -95,7 +95,11 @@ export class PanelNavigation {
    */
   select(panelId) {
     if (this._destroyed) return;
-    this._setPanelCollapsed(panelId, this._store.isOpen(panelId), {
+    // The panel itself, not the store: the store follows its class a
+    // microtask later, after a same-task setPanelCollapsed.
+    const panel = document.getElementById(panelId);
+    if (!panel) return;
+    this._setPanelCollapsed(panelId, !panel.classList.contains('collapsed'), {
       explicit: true,
     });
   }

src/ui/panelNavigation.test.mjs

@@ -103,6 +103,18 @@ test('selecting an item toggles its panel explicitly', async () => {
   ui.destroy();
 });
 
+test('selecting right after a same-task collapse reads the panel, not the store', async () => {
+  const { left, calls, ui, navigation } = setup();
+  await nextTick();
+  // A host collapses Data Layers and selects its item in one task, before
+  // the store follows the class change.
+  left.querySelector('#data-panel').classList.add('collapsed');
+  navigation.select('data-panel');
+  assert.deepEqual(calls, [['data-panel', false, { explicit: true }]]);
+  navigation.destroy();
+  ui.destroy();
+});
+
 test('the rails follow disclosure and availability changes', async () => {
   const { left, right, ui, navigation } = setup();
   document.getElementById('data-panel').classList.add('collapsed');