Durability and Serialization

Design a binary serialization format to save the HNSW graph and vector data to a single file.

Implement a function to serialize the in-memory graph state to a memory-mapped file.

Implement a function to load a serialized graph from a file back into memory, reconstructing the data structures.

Design and implement a Write-Ahead Log (WAL) to record operations like vector insertions before they are committed to the main graph structure.

Implement a recovery routine that replays the WAL upon startup to restore the database to a consistent state after a simulated crash.

Write a test to verify the integrity of the restored data after a crash and recovery cycle.