indent and space a directory's sessions

The rows sat flush against their own heading and against the next directory, so an expanded node ran into
its neighbours as one undifferentiated column — the tree stopped reading as a hierarchy at exactly the
moment it had one.

pl-8 lines the rows up under the heading's TEXT rather than under its chevron, which is what makes "these
belong to that" legible without drawing a guide line, and py-2 separates the group from the headings above
and below it.

src/workspaces/officerdev/src/apps/ChatHistory/SessionTree.tsx

@@ -112,14 +112,22 @@ const DirectoryNode = ({ pwd, home, expanded, onToggle, live, activeId, actions
         </button>
       </div>
 
+      {/*
+        Inset, and breathing room top and bottom.
+
+        The rows sat flush against their own directory heading and against the next one, so an expanded node
+        ran into its neighbours as one undifferentiated column and the tree stopped reading as a hierarchy at
+        exactly the moment it had one. The left inset lines the rows up under their heading's TEXT rather than
+        under its chevron, which is what makes "these belong to that" legible without a guide line.
+      */}
       {expanded && (
-        <div className="bg-background/40">
+        <div className="bg-background/40 py-2 pl-8">
           {isLoading && sessions.length === 0 ? (
             <LoadingBlock label="Reading transcripts…" />
           ) : sessions.length === 0 ? (
             // Reachable: `/chat/pwds` counts transcripts per group, and a group can hold only files this
             // reader skips. Better than an accordion that opens onto nothing.
-            <div className="px-9 py-3 text-xs text-muted-foreground">No readable conversations here.</div>
+            <div className="py-3 text-xs text-muted-foreground">No readable conversations here.</div>
           ) : (
             <DataList className="!h-auto !overflow-visible">
               {sessions.map((session) => (