Module delta 

In-memory delta for buffering vector writes before flush.

This module implements the delta pattern for accumulating vector writes in memory before they are atomically flushed to storage.

Key Design

• The VectorDbDeltaContext contains shared state: the in-memory ID dictionary (DashMap), the centroid graph for assignment, and a sync-safe ID allocator
• The delta handles all write logic in apply(): ID allocation, dictionary lookup for upsert detection, centroid assignment, and dictionary updates
• The write path just validates and enqueues

WriteCoordinator Integration

The VectorDbWriteDelta implements the Delta trait for use with the WriteCoordinator. The delta receives VectorWrite instances and handles ID allocation, dictionary updates, and centroid assignment.

Structs

VectorDbImmutableDelta

Immutable delta containing all RecordOps ready to be flushed.