Shared 512-token chunking module for the OB1/vault embedding stack.
Wraps tiktoken cl100k_base; consumed by vault_mcp, ob1-enricher,
ob1-reflector before passing to Ollama (nomic-embed-text, 768-d).
Extracted from /opt/projects/homelab/shared/python/embedding_chunking
to its own repo so consumers can pin via git ref instead of editable
path source, unblocking docker builds outside the homelab tree.
