UX: Full viewport composer layout on iPad

Partially reverts 94ab48c by using Safari hacks on iPad again.

This brings parity in the composer UI between iPhones and iPads

Hides grippie and fullscreen toggle button when the keyboard is visible on iPads

app/assets/javascripts/discourse/lib/safari-hacks.js.es6

@@ -75,7 +75,7 @@ export function isWorkaroundActive() {
 function positioningWorkaround($fixedElement) {
   const caps = Discourse.__container__.lookup("capabilities:main");
 
-  if (!caps.isIOS || caps.isIpadOS || safariHacksDisabled()) {
+  if (!caps.isIOS || safariHacksDisabled()) {
     return;
   }
 

app/assets/stylesheets/desktop/compose.scss

@@ -230,6 +230,16 @@ a.toggle-preview {
   text-align: right;
 }
 
+html.keyboard-visible {
+  .grippie,
+  &:not(.fullscreen-composer) .toggle-fullscreen {
+    display: none;
+  }
+  #reply-control.open {
+    height: calc(var(--composer-vh, 1vh) * 100);
+  }
+}
+
 // fullscreen composer styles
 .fullscreen-composer {
   overflow: hidden;
@@ -282,9 +292,3 @@ a.toggle-preview {
     }
   }
 }
-
-.fullscreen-composer.keyboard-visible {
-  #reply-control.fullscreen {
-    top: 0px;
-  }
-}