Press once whatever a second press would open over or undo

The browser plugin runs every call on a page again when its first
attempt takes over a second, and on the runner a press can. For most
presses that costs nothing. For two kinds it breaks the test: a press
that opens a dialog, a sheet, a full-screen view or a modal rail over
its own trigger, whose second press can never land, and a press that
changes state a second one would change again — a menu trigger, a
toggle, a chip, a range picker's day, a paging key, a Save. The bottom
sheet with preset heights timed out on WebKit that way after the date
picker had on Firefox.

Every such press in the browser suite now goes through pressOnce(), 253
of them across sixteen files, not only the ones the runner happened to
catch; focus moves inside an open view, Escape, links and plain "set"
actions keep the retry, which is harmless for them.

Two samples that were still racing the machine:

- The standard side sheet's exit is caught half-way with its motion
  stretched, as every other mid-exit sample is, and fullSpeed() takes
  the stretch off again before the test times a reopen against the real
  exit. Under load on Linux WebKit it had failed two runs in five; it
  passes ten in ten.
- The switch-and-checkbox row measures its widths once, so it now waits
  for the resize to land and the brand face to load before it does.

Browser 300 passed on Firefox and WebKitGTK in a Linux container held to
two busy cores, and on Chrome, Firefox and WebKit on macOS. Feature 1159
passed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/Browser/LayoutTest.php

@@ -250,8 +250,11 @@ it('shows the list alone below expanded, and the detail with a back button once
     $page = listDetailPage(599);
 
     $page->script("document.querySelector('a[href=\"#message-2\"]').focus()");
-    $page->keys('a[href="#message-2"]', 'Enter')
-        ->assertSeeIn('#selected', '2')
+
+    // The selected item's link is hidden once the detail pane covers it: pressOnce(), tests/Pest.php.
+    pressOnce($page)->keys('a[href="#message-2"]', 'Enter');
+
+    $page->assertSeeIn('#selected', '2')
         ->assertSeeIn('#detail-text', 'The message')
         ->assertScript('! '.listDetailVisible(LIST_PANE))
         ->assertScript(listDetailVisible(DETAIL_PANE))
@@ -259,8 +262,10 @@ it('shows the list alone below expanded, and the detail with a back button once
         ->assertScript("document.activeElement === document.querySelector('".DETAIL_PANE."')")
         ->assertScript("document.querySelector('".DETAIL_PANE." [data-md-list-detail-back] button').checkVisibility()");
 
-    $page->click(DETAIL_PANE.' [data-md-list-detail-back] button')
-        ->assertSeeIn('#selected', 'NULL')
+    // The back button closes the detail pane: pressOnce(), tests/Pest.php.
+    pressOnce($page)->click(DETAIL_PANE.' [data-md-list-detail-back] button');
+
+    $page->assertSeeIn('#selected', 'NULL')
         ->assertScript(listDetailVisible(LIST_PANE))
         ->assertScript('! '.listDetailVisible(DETAIL_PANE))
         // And back to the item it came from.
@@ -303,8 +308,10 @@ it('mirrors the list-detail in a right-to-left document', function () {
 
     $page = listDetailPage(599, 'rtl');
 
-    $page->click('a[href="#message-1"]')
-        ->assertSeeIn('#selected', '1')
+    // The selected item's link is hidden once the detail pane covers it: pressOnce(), tests/Pest.php.
+    pressOnce($page)->click('a[href="#message-1"]');
+
+    $page->assertSeeIn('#selected', '1')
         ->assertScript("getComputedStyle(document.querySelector('".DETAIL_PANE." [data-md-list-detail-back] svg')).transform !== 'none'");
 });
 
@@ -321,14 +328,18 @@ it('selects from Alpine through x-model, with the layout\'s own back row', funct
 
     $page = layoutPage($body, 599);
 
-    $page->click('#pick')
-        ->assertSeeIn('#chosen', 'b')
+    // The list pane is hidden once the button that picks it is covered: pressOnce(), tests/Pest.php.
+    pressOnce($page)->click('#pick');
+
+    $page->assertSeeIn('#chosen', 'b')
         ->assertSeeIn('#shown', 'b')
         ->assertScript('! '.listDetailVisible(LIST_PANE))
         ->assertScript("document.querySelector('[data-md-list-detail-back-row]').checkVisibility()");
 
-    $page->click('[data-md-list-detail-back-row] button')
-        ->assertSeeIn('#chosen', 'null')
+    // The back button closes the detail pane: pressOnce(), tests/Pest.php.
+    pressOnce($page)->click('[data-md-list-detail-back-row] button');
+
+    $page->assertSeeIn('#chosen', 'null')
         ->assertScript(listDetailVisible(LIST_PANE))
         ->assertScript("document.activeElement === document.querySelector('#pick')");
 });
@@ -386,8 +397,10 @@ it('docks the supporting pane as a bottom sheet below expanded, opened and close
         ->assertScript(layoutRect(SUPPORTING_SIDE, 'bottom').' === window.innerHeight')
         ->assertScript(layoutStyle(SUPPORTING_SIDE, 'borderTopLeftRadius')." === '28px'");
 
-    $page->click($handle)
-        ->assertAttribute($handle, 'aria-expanded', 'true')
+    // The handle toggles the sheet on every press: pressOnce(), tests/Pest.php.
+    pressOnce($page)->click($handle);
+
+    $page->assertAttribute($handle, 'aria-expanded', 'true')
         ->assertScript("document.querySelector('#comment').checkVisibility()")
         ->assertScript(layoutRect(SUPPORTING_SIDE, 'bottom').' === window.innerHeight');
 
@@ -560,8 +573,10 @@ it('shows each canonical layout working on its own Layout page', function () {
 
     $compactListDetail = layoutReady(visit('/material/layout/list-detail')->resize(599, 900));
 
-    $compactListDetail->click('#example-list-detail a:has-text("Chiara Rossi")')
-        ->assertSeeIn('#example-list-detail [data-md-list-detail-pane="detail"]', 'Train times for Friday')
+    // The selected item's link is hidden once the detail pane covers it: pressOnce(), tests/Pest.php.
+    pressOnce($compactListDetail)->click('#example-list-detail a:has-text("Chiara Rossi")');
+
+    $compactListDetail->assertSeeIn('#example-list-detail [data-md-list-detail-pane="detail"]', 'Train times for Friday')
         ->assertScript("! document.querySelector('#example-list-detail [data-md-list-detail-pane=\"list\"]').checkVisibility()")
         ->assertNoJavaScriptErrors();