fix+upstream: hooks-order crash, ConfirmDialog/PageHeader/skeletons, styled error boundary

Hoists hooks above early return (render-time Navigate); ports finance's
ConfirmDialog/PageHeader/loading/states + APC error-copy mapper; removes
window.confirm, dead appbar search, and seeded fake notifications; wires toasts.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/routes/assistant.tsx

@@ -111,6 +111,7 @@ import { TypingIndicator } from "@crema/chat-ui"
 import { CommandBar } from "@crema/aifirst-ui"
 
 import { AppShell } from "~/components/layout/app-shell"
+import { ConfirmDialog } from "~/components/confirm-dialog"
 import { MessageBody } from "~/components/assistant/message-body"
 import { Button } from "~/components/ui/button"
 import {
@@ -1956,20 +1957,32 @@ function ThreadsPicker({
               >
                 <Pencil className="size-3.5" />
               </button>
-              <button
-                type="button"
-                data-action={`assistant-thread-delete-${t.id}`}
-                onClick={() => {
+              <ConfirmDialog
+                trigger={
+                  <button
+                    type="button"
+                    data-action={`assistant-thread-delete-${t.id}`}
+                    disabled={threads.length <= 1}
+                    className="rounded p-1 text-muted-foreground opacity-0 hover:bg-destructive/10 hover:text-destructive group-hover:opacity-100 disabled:cursor-not-allowed disabled:opacity-30"
+                    title={
+                      threads.length <= 1
+                        ? "Can't delete the last conversation"
+                        : "Delete"
+                    }
+                    aria-label="Delete"
+                  >
+                    <Trash2 className="size-3.5" />
+                  </button>
+                }
+                title="Delete conversation?"
+                description={`"${t.title}" and its messages will be permanently removed.`}
+                confirmLabel="Delete"
+                destructive
+                onConfirm={() => {
                   if (threads.length <= 1) return
-                  if (window.confirm(`Delete "${t.title}"?`)) onDelete(t.id)
+                  onDelete(t.id)
                 }}
-                disabled={threads.length <= 1}
-                className="rounded p-1 text-muted-foreground opacity-0 hover:bg-destructive/10 hover:text-destructive group-hover:opacity-100 disabled:cursor-not-allowed disabled:opacity-30"
-                title="Delete"
-                aria-label="Delete"
-              >
-                <Trash2 className="size-3.5" />
-              </button>
+              />
             </div>
           )
         })}