Address the /code-review high finding on S5b: gating the info-page cast enrich on
`people_enriched_at is None` removed the old per-view regrow of `cast_names`, so a routine full sync
that reset it to the listing top-20 (`_apply_facet_fields`) — while never clearing people_enriched_at —
left it permanently truncated, silently dropping cast past the top ~20 from the S4 person-page filter.
Root fix: `_apply_facet_fields` now only takes the listing's cast for a NOT-yet-enriched row; an
enriched row keeps its fuller stored cast (people_text still rebuilt from the updated directors + the
preserved cast). Makes the people_enriched_at flag the endpoints/backfill trust actually reliable.
Tests: cast_names preserved for an enriched row vs applied for a fresh one; show_detail lazy-fill
persists imdb/full_cast on first view. Full suite green.
peter
81827fcf28