feat(app): open the workspace actions menu as a sheet on compact

The trigger was a vertical ellipsis on compact and a horizontal one elsewhere.
Use the horizontal glyph everywhere: it is the wider shape, and it is the one
sitting above a menu that now presents from the bottom edge.

The button draws at 32pt, under the 44pt touch minimum, and three of them sit
flush beside the title, so the slop can only grow vertically — widening it
would put two buttons' hit areas over the same pixels.

packages/app/src/screens/workspace/workspace-screen.tsx

@@ -26,7 +26,6 @@ import {
   ChevronDown,
   Copy,
   Ellipsis,
-  EllipsisVertical,
   Globe,
   Import as ImportIcon,
   PanelRight,
@@ -246,7 +245,6 @@ function buildWorkspaceFileLocation(
 
 const ThemedLoadingSpinner = withUnistyles(LoadingSpinner);
 const ThemedEllipsis = withUnistyles(Ellipsis);
-const ThemedEllipsisVertical = withUnistyles(EllipsisVertical);
 const ThemedChevronDown = withUnistyles(ChevronDown);
 const ThemedCopy = withUnistyles(Copy);
 const ThemedRotateCw = withUnistyles(RotateCw);
@@ -1045,18 +1043,16 @@ function HeaderMenuProfileItem({
   );
 }
 
-function WorkspaceHeaderMenuTriggerIcon({
-  hovered,
-  open,
-  isMobile,
-}: {
-  hovered: boolean;
-  open: boolean;
-  isMobile: boolean;
-}) {
-  const Icon = isMobile ? ThemedEllipsisVertical : ThemedEllipsis;
+/**
+ * The compact header buttons draw at 32pt, under the 44pt touch minimum, and sit flush against
+ * each other — so the slop can only grow vertically. Widening it would put two buttons' slop over
+ * the same pixels, which is a worse miss than a small target.
+ */
+const COMPACT_HEADER_BUTTON_HIT_SLOP = { top: 8, bottom: 8 } as const;
+
+function WorkspaceHeaderMenuTriggerIcon({ hovered, open }: { hovered: boolean; open: boolean }) {
   const colorMapping = hovered || open ? foregroundColorMapping : mutedColorMapping;
-  return <Icon size={16} uniProps={colorMapping} />;
+  return <ThemedEllipsis size={16} uniProps={colorMapping} />;
 }
 
 function WorkspaceHeaderMenu({
@@ -1097,22 +1093,28 @@ function WorkspaceHeaderMenu({
 
   const renderTriggerIcon = useCallback(
     ({ hovered, open }: { hovered: boolean; open: boolean }) => (
-      <WorkspaceHeaderMenuTriggerIcon hovered={hovered} open={open} isMobile={isMobile} />
+      <WorkspaceHeaderMenuTriggerIcon hovered={hovered} open={open} />
     ),
-    [isMobile],
+    [],
   );
 
   return (
-    <DropdownMenu>
+    <DropdownMenu compactMode="sheet">
       <DropdownMenuTrigger
         testID="workspace-header-menu-trigger"
         style={isMobile ? styles.compactHeaderActionButton : styles.headerActionButton}
+        hitSlop={isMobile ? COMPACT_HEADER_BUTTON_HIT_SLOP : undefined}
         accessibilityRole="button"
         accessibilityLabel={t("workspace.header.actions.workspaceActions")}
       >
         {renderTriggerIcon}
       </DropdownMenuTrigger>
-      <DropdownMenuContent align="start" width={220} testID="workspace-header-menu">
+      <DropdownMenuContent
+        align="start"
+        width={220}
+        testID="workspace-header-menu"
+        sheetTitle={t("workspace.header.actions.workspaceActions")}
+      >
         <DropdownMenuItem
           testID="workspace-header-new-agent"
           leading={menuNewAgentIcon}