Function resolve_toml_phases 

async fn resolve_toml_phases(
    provider: &impl Provider,
    params: &WriteProposalParams,
) -> Result<(PhaseToml, PhaseToml)>

Resolve schedule/execute Safe addresses and nonces, then compute all hashes.

Fails loudly if the signer set is ambiguous or the nonce query fails; a partial proposal.toml would be unverifiable and must not be written.