fix(clients): Show Completed toggle did nothing for tasks older than 7 days

The default task fetch (/api/clients/[id]/tasks) already excludes
completed/cancelled/NA tasks older than a 7-day cutoff server-side. The
"Show Completed" button only filtered the in-memory task list, so if all
completed tasks were older than a week, toggling it revealed nothing —
they were never fetched.

Wire the toggle to re-fetch with archived=true (bypasses the cutoff) when
turning it on, and revert to the default filtered fetch when turning it
back off, so it doesn't leak dead-policy tasks into the non-completed view.

ondeck/src/components/clients/client-detail.tsx

@@ -112,6 +112,16 @@ export function ClientDetail({ client, designations, policyGroups = [], allPolic
     refreshTasks(next)
   }
 
+  const handleToggleCompleted = () => {
+    const next = !showCompleted
+    setShowCompleted(next)
+    // The default (non-archived) task fetch only includes completed/cancelled/NA tasks
+    // from the last 7 days — anything older needs the archived fetch to actually load.
+    // Revert to the filtered fetch when turning it back off (unless Show Archived is
+    // separately on) so dead-policy tasks pulled in by the archived fetch don't leak in.
+    if (!showArchivedTasks) refreshTasks(next)
+  }
+
   // Assignments state
   const [allUsers, setAllUsers] = useState<SimpleUser[]>([])
   const [claimsUsers, setClaimsUsers] = useState<SimpleUser[]>([])
@@ -647,7 +657,7 @@ export function ClientDetail({ client, designations, policyGroups = [], allPolic
 
             {/* Show completed toggle */}
             <button
-              onClick={() => setShowCompleted((v) => !v)}
+              onClick={handleToggleCompleted}
               className={`flex items-center gap-1.5 px-3 py-1.5 rounded transition-colors font-medium ${
                 showCompleted
                   ? 'bg-primary text-primary-foreground'