Ensure Namespace Payload Indexes

(Re-)create the namespace's declared payload indexes in the vector store, including FULLTEXT/BM25, idempotently. ZERO-EXTRACTION: registers any missing indexes and backfills existing documents WITHOUT triggering any ingest or re-extraction. Use to repair a missing index (e.g. a FULLTEXT index that failed to register) or as a self-serve re-index tool — no re-ingest, no GPU.

READING THE RESPONSE: ensured lists indexes the call confirmed present — it does NOT mean they were newly built, and an already-registered index is a cheap no-op on the shard. rebuilt is populated only with force_rebuild=true, which is the case that does real work. skipped is normally empty because the store reports an idempotent no-op as success rather than an error, so an empty skipped does not imply the rest were created. created is a deprecated alias of ensured + rebuilt.

COST: a plain ensure is cheap. force_rebuild=true applies to EVERY declared index, drops and rebuilds each from the complete store, and for FULLTEXT fields first hydrates the full payload store — no GPU, but real shard CPU and memory proportional to the corpus. Size it before running on a large or memory-constrained namespace.