fn tempo_chain_needing_auth(url: &Url, resp: &Response) -> Option<u64>Expand description
Returns Some(chain_id) when a 402 response should trigger the
wallet.tempo.xyz device-code authorization flow.
Conditions: known Tempo endpoint, interactive (TTY, not CI), and no
offered Tempo challenge resolves against a local key on (chain, currency).
The picked chain matches the first unresolved challenge — same iteration
order MppHttpTransport::select_challenge uses.