fix(client): preserve sidebar drag ordering

packages/client/ui-workspace/src/client/WorkspaceBrowser.module.css

@@ -299,7 +299,9 @@
   margin-left: -4px;
   margin-right: calc(-1 * var(--dsh-session-list-edge-inset));
   padding-left: 4px;
-  overflow: hidden;
+  /* The list remains the scroll clip. This seat stays visible so the
+     absolutely positioned first-boundary marker can occupy the header gap. */
+  overflow: visible;
 }
 
 .rail .listArea {
@@ -387,6 +389,7 @@
   margin-top: 4px;
 }
 
+.listTopDropIndicator,
 .workspaceDropBefore::before,
 .workspaceDropAfter::after {
   content: '';
@@ -408,6 +411,18 @@
   pointer-events: none;
 }
 
+/* The first insertion boundary keeps the same -8px coordinate as every
+   Workspace boundary, but lives outside the scrolling clip. */
+.listTopDropIndicator {
+  top: -8px;
+  left: -4px;
+  right: calc(var(--dsh-session-list-edge-inset) + 4px);
+}
+
+.listTopDropActive > .workspaceDropBefore:first-child::before {
+  display: none;
+}
+
 .workspaceDropBefore::before {
   top: -8px;
 }

packages/client/ui-workspace/src/client/WorkspaceBrowser.tsx

@@ -299,15 +299,13 @@ function SessionTree({
       ? group.sessions.length
       : group.sessions.findIndex(session => session.id === anchor)
     if (sourceIndex !== -1 && (anchorIndex === sourceIndex || anchorIndex === sourceIndex + 1)) return
-    if (orderBy === 'updated') {
-      const account = orderedWorkspaces.find(workspace => workspace.workspaceId === activeDrag.workspaceId)
-      if (account === undefined) return
-      const nextOrder = account.sessionIds.filter(id => id !== activeDrag.sessionId)
-      const insertAt = anchor === undefined ? nextOrder.length : nextOrder.indexOf(anchor)
-      nextOrder.splice(insertAt === -1 ? nextOrder.length : insertAt, 0, activeDrag.sessionId)
-      setRecentSessionOrder(activeDrag.workspaceId, nextOrder.map(id => id as string))
-      return
-    }
+    const account = orderedWorkspaces.find(workspace => workspace.workspaceId === activeDrag.workspaceId)
+    if (account === undefined) return
+    const nextOrder = account.sessionIds.filter(id => id !== activeDrag.sessionId)
+    const insertAt = anchor === undefined ? nextOrder.length : nextOrder.indexOf(anchor)
+    nextOrder.splice(insertAt === -1 ? nextOrder.length : insertAt, 0, activeDrag.sessionId)
+    setRecentSessionOrder(activeDrag.workspaceId, nextOrder.map(id => id as string))
+    if (orderBy === 'updated') return
     insertSessionBefore(activeDrag.workspaceId, activeDrag.sessionId, anchor).catch((reason: unknown) => {
       console.warn('session reorder rejected:', reason)
     })
@@ -332,10 +330,18 @@ function SessionTree({
       console.warn('workspace reorder rejected:', reason)
     })
   }
+  const workspaceDropAtListStart = groups[0]?.workspaceId !== undefined
+    && workspaceDrag?.over?.id === groups[0].workspaceId
+    && workspaceDrag.over.half === 'before'
 
   return (
     <div className={clsx(css.treeBody, css.wide)}>
-      <div className={css.list} role="tree" aria-label={t('section.sessions')}>
+      {workspaceDropAtListStart && <span className={css.listTopDropIndicator} aria-hidden="true" />}
+      <div
+        className={clsx(css.list, workspaceDropAtListStart && css.listTopDropActive)}
+        role="tree"
+        aria-label={t('section.sessions')}
+      >
         {groups.length === 0 && (
           <div className={css.empty}>{t('empty.none')}</div>
         )}