feat(bet1): productionize reuse-under-drift + validate on a real learned-GNN trajectory (ADR-202 WIN)

crates/ruvector-diskann/Cargo.toml

@@ -11,6 +11,8 @@ description = "DiskANN/Vamana — SSD-friendly approximate nearest neighbor sear
 default = []
 gpu = []  # Feature flag for GPU acceleration (CUDA/Metal stubs)
 simd = ["simsimd"]
+# BET 1 (ADR-200): fixed-topology reuse + periodic rebuild under metric drift.
+reuse-under-drift = []
 
 [dependencies]
 memmap2 = { workspace = true }

crates/ruvector-diskann/src/lib.rs

@@ -15,7 +15,12 @@ pub mod error;
 pub mod graph;
 pub mod index;
 pub mod pq;
+/// Fixed-topology reuse + periodic rebuild under metric drift (BET 1, ADR-200).
+#[cfg(feature = "reuse-under-drift")]
+pub mod reuse;
 
 pub use error::{DiskAnnError, Result};
 pub use index::{DiskAnnConfig, DiskAnnIndex};
 pub use pq::ProductQuantizer;
+#[cfg(feature = "reuse-under-drift")]
+pub use reuse::{DriftingIndex, RebuildPolicy, RecallTrigger};