do not render the frame before its session exists

Saving the connection showed an error that a refresh then cleared. The effect
that re-mints the frame session re-ran, but `state` was left at 'ready' from
the previous pass — so the iframe mounted immediately, before the cookie
existed, and the first request inside it answered 401. By the time anyone
refreshed, the mint had finished.

A stale 'ready' is worse than a spinner: it renders something broken
confidently.

Also stays on the form after the URL-only step, where there is still a token to
set. Bouncing to a frame that immediately sends you back is worse than not
moving.

web/GiteaConnection.tsx

@@ -81,10 +81,16 @@ export const GiteaConnection = ({ state, onSaved }: Props) => {
     setError(null);
     try {
       await put('/gitea/_config', state.isOwner === false ? { token } : { url, token });
+      // ORDER MATTERS. `onSaved` re-reads the connection and re-mints the frame session; navigating
+      // first would swap to the frame while that is still in flight, and the frame would load against a
+      // session that does not exist yet.
       onSaved();
       // Back to the frame. Saving from `/gitea/connection` otherwise leaves you looking at the form you
       // just submitted, which reads as nothing having happened.
-      navigate('/gitea');
+      //
+      // Only when there is a frame to go back TO: after the URL-only step there is still a token to
+      // set, and bouncing to a frame that immediately sends you back is worse than staying put.
+      if (!needsUrl) navigate('/gitea');
     } catch (err) {
       setError(err instanceof Error ? err.message : 'could not save');
     } finally {