Re-read .env/environment, re-probe credentials, and continue.
Runs the same environment/credential reload core as the /reload
command (reload_from_environment + clear_caches), so a credential
env var added to a .env file after launch is picked up without a full
restart; it intentionally skips /reload's theme and skill
re-discovery. If the provider was blocked and is now resolvable, dismiss
with SAVED so the caller retries the original operation; otherwise
refresh the modal in place and toast the outcome.
