Building the summary through `_build_api_kwargs` means it now carries
`tools`, but it still skipped the `_sanitize_structure_surrogates` /
`_force_ascii_payload` chokepoint the main loop applies after building
(turn_api_request). On cache-planned routes the main loop scrubs a deep
copy of the tools, so `agent.tools` can still hold a lone surrogate that
providers reject with a non-retryable 400 (#50959 class) — a request the
tool-less summary never used to make. Apply the same two passes here.
kshitijk4poor
53cfca9766