Fade and shrink popovers out in every engine, Firefox included

Menus, submenus, tooltips, rich tooltips and the FAB menu held their
exit with `transition-behavior: allow-discrete` on `display` and
`overlay`. Firefox transitions neither (MDN browser-compat-data,
`display.is_transitionable`: Chrome 117, Safari 18, Firefox none), so
every one of them vanished on its first frame there. A script cannot
hold a popover open instead: `beforetoggle` is not cancellable on the
way out, and the browser's own light dismiss (Escape, a press outside)
never asks.

resources/js/popover-exit.js: a popover marked `data-md-popover-exit`
closes for real at once — focus, aria-expanded and toggle stay the
browser's — and a copy taken in `beforetoggle`, while it is still drawn,
stands in for the exit. The copy is decoration: a manual popover in the
top layer (closing no other popover), inert, aria-hidden, without ids or
nested popovers, `x-ignore`d so Alpine starts nothing in it, pinned to
the popover's box with its resolved colours. It is shown with its
transitions off, so `@starting-style` does not replay the entry, then
marked `data-md-popover-closing`, which each stylesheet turns into its
closed values (`:popover-open:not([data-md-popover-closing])`, and the
FAB menu's items' sink), so it moves on the component's own tokens. It
is removed once the longest of them has run, and opening the popover
again takes it away. Under reduced motion every duration is zero and no
copy is made. `display`, `overlay` and `allow-discrete` leave the
transitions, so Chrome and Safari take the same path.

Browser tests in Chrome, Firefox and Safari slow the motion tokens so a
round trip still finds the exit on screen: a menu after Escape and after
a press outside (the real menu closed and focus back on its button, the
copy inert, fading, with no Alpine state, and gone after), a reopen
part-way through, reduced motion, a submenu while its menu stays open, a
tooltip, the FAB menu's items part-way down their sink, and a persistent
rich tooltip.

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

tests/Feature/Components/TooltipTest.php

@@ -10,7 +10,7 @@ it('wraps a trigger and anchors the bubble to it', function () {
     expect($anchor)->not->toBeEmpty()
         ->and($html)
         ->toMatch('/<span data-md-tooltip-anchor style="anchor-name: --material-tooltip-[a-z0-9]+">\s*<button>Copy<\/button>/')
-        ->toMatch('/<span\s+popover="manual"\s+aria-hidden="true"\s+x-data="materialTooltip"\s+data-md-tooltip\s+data-md-side="top"\s+style="position-anchor: '.preg_quote($anchor[1], '/').'"\s*>Copy link<\/span>/')
+        ->toMatch('/<span\s+popover="manual"\s+aria-hidden="true"\s+x-data="materialTooltip"\s+data-md-tooltip\s+data-md-popover-exit\s+data-md-side="top"\s+style="position-anchor: '.preg_quote($anchor[1], '/').'"\s*>Copy link<\/span>/')
         ->not->toContain('class=');
 });
 
@@ -44,12 +44,14 @@ it('draws M3\'s plain tooltip in the inverse surface, and fades on the effects s
         'font' => 'var(--md-sys-typescale-body-sm)',
         'pointer-events' => 'none',
         'opacity' => '0',
+        'transition-property' => 'opacity',
         'transition-duration' => 'var(--md-sys-motion-effects-fast-duration)',
         'transition-timing-function' => 'var(--md-sys-motion-effects-fast)',
-        'transition-behavior' => 'allow-discrete',
     ])
-        ->and($css->declarations('[data-md-tooltip]:popover-open'))->toBe(['opacity' => '1'])
-        ->and($css->declarations('[data-md-tooltip]:popover-open', ['@starting-style']))->toBe(['opacity' => '0']);
+        // No `display`/`overlay` transition: the fade out is the exit copy's (popover-exit.js).
+        ->not->toHaveKey('transition-behavior')
+        ->and($css->declarations('[data-md-tooltip]:popover-open:not([data-md-popover-closing])'))->toBe(['opacity' => '1'])
+        ->and($css->declarations('[data-md-tooltip]:popover-open:not([data-md-popover-closing])', ['@starting-style']))->toBe(['opacity' => '0']);
 });
 
 it('takes the caller\'s class and style on the standalone wrapper, its root', function () {