Fix refresh_token cookie never actually being written

st.rerun() immediately after cookie_manager.set(...) aborted the
script run before the browser could mount the cookie-manager's 'set'
component and run the JS that actually writes document.cookie --
so the encrypted refresh_token never reached the browser, and every
later visit correctly (if uselessly) reported no cookie present.
Removed the rerun; the callback already updates session_state
directly, so the rest of this same run (sidebar, page) already
reflects the fresh access token without needing to restart the script.

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

app.py

@@ -75,7 +75,12 @@ def _handle_drive_oauth_callback(cookie_manager) -> None:
         cookie_token_store.save_refresh_token(cookie_manager, st.user.email, refresh_token)
     _store_access_token(tokens)
     st.query_params.clear()
-    st.rerun()
+    # Deliberately no st.rerun() here: it would abandon this script run before
+    # the browser has a chance to mount the cookie-manager's "set" component
+    # and actually execute the JS that writes document.cookie, so the saved
+    # refresh_token would never actually reach the browser. Letting this run
+    # finish naturally still reflects the fresh access token immediately,
+    # since the rest of app.py (sidebar, page) renders right after this call.
 
 
 def _ensure_drive_access(cookie_manager) -> None: