Fixed

• Fixed a race where segment files could be deleted while still memory-mapped by active searchers. MMapDirectory now reference-counts open IndexInput instances and defers deletion until the final mapping is released.
• Added retry handling for transient Windows file-lock failures during mapped-file deletion and atomic segments_N publication.
• Added permanent commit/search churn regression coverage based on repeated update, commit, refresh, delete and search cycles.

These fixes came from a detailed real-world stability report and reproduction by Apophis (@FreeApophis) in #34. Thanks for sticking with the investigation and providing the workload that exposed the Windows segment-lifecycle races.