Three surgical import changes. No behavior change. No new semantics.
Backend decides Rust vs pure-Python transparently.
- field/propagate.py: versor_apply <- algebra.backend
- vocab/manifold.py: cga_inner <- algebra.backend
- vault/store.py: recall loop replaced with vault_recall() from
algebra.backend; public result shape preserved ({versor, score,
metadata, index}). null_project stays on algebra.cga (not the
recall hot path). store() and reproject() unchanged.
Rust path for vault_recall uses Rayon parallel scan and releases
the GIL. Python fallback is sequential and behaviorally identical.
No batching introduced; that is Commit 3+.
