P2 measured that the producer's payload now carries title/req_number/sources/source_* on
every excerpt (14 members, was 9), but PrepassExcerpt ignored them (extra="ignore") and
_data_blocks rendered only concept_id/adjudication/trust_tier -- so (b') was a po verdict,
never a model verdict. title/req_number/sources are now named fields; source_* locators are
read via model_extra and a prefix scan (measured: the producer treats source_* as an
open-ended family, not a fixed allowlist), so a future producer's new source_foo key reaches
the prompt without a code change here. A P1-form payload renders byte-identical to before.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
