Manticore Search 29.9.0: Chunked auto-embeddings and mmap columnar access

Manticore Search 29.9.0 is out.

Long documents no longer have to fit into one embedding: split them into chunks, keep multiple vectors per document, and search each chunk independently with KNN.

Also in this release: mmap columnar access by default, UTF-8 identifiers, embedding workload controls, and fixes across hybrid search, bulk ingestion, grouping, and backups.