DR-052 — hybrid_search's positional-param set is capped at the Task-144 shape

The polymorphic hybrid_search RPC grew 7→12 positional params in one Task; the set is CAPPED at the Task-144 shape. The next filter axis triggers a deliberate contract-evolution decision — strictly-validated jsonb filters (MUST RAISE on unknown keys; silent-ignore reproduces the OBS-4 dead-filter class) or a versioned hybrid_search_v2 — never a 13th positional param. Binds id-162 (the keyword facet, the first axis to hit the cap). Provenance: S460 staff-engineer review of OQ-144-2 (specs/id-144-hybrid-search-completion/notes/s460-oq144-2-staff-review.md — migrated S507 out of canonical’s gitignored scratch; the S504 F1 lossy-provenance caveat no longer applies).

(Swept unrecorded at ec9fcfde; re-accepted by owner ruling S499 — the S499 tombstone audit found it still binding with no other home.)