fix(cli): show Resuming... banner immediately on thread resume (#3297)

Lifts the one-line `_resume_thread_intent` check from PR #3193 onto
`main` so the fix can ship independently. Once #3193 merges `main` back
in, this diff will collapse into the existing v0.6 change with no
conflict.

`WelcomeBanner` was given `defer_connecting_display=self._connecting`,
which suppresses the connecting footer entirely while `_connecting` is
`True` — that path also runs for `deepagents -r` / `/thread` resumption,
so the "Resuming..." footer never rendered until the connect finished.
Gating the defer on `self._resume_thread_intent is None` lets the resume
path show its banner immediately while leaving the cold-start connect
behavior unchanged.

Co-authored-by: Sydney Runkle <sydneymarierunkle@gmail.com>

libs/cli/deepagents_cli/app.py

@@ -1616,7 +1616,8 @@ class DeepAgentsApp(App):
                 connecting=self._connecting,
                 resuming=self._resume_thread_intent is not None,
                 local_server=self._server_kwargs is not None,
-                defer_connecting_display=self._connecting,
+                defer_connecting_display=self._connecting
+                and self._resume_thread_intent is None,
                 id="welcome-banner",
             )
             yield Container(id="messages")