v0.2.0

Added

• Stats(cfg) — scan cache directory and return total size/file count without mmap
• Clear(cfg) — remove all cached files and empty directories
• Trim(cfg, maxSize, maxFiles, maxAge) — LRU eviction by size, file count, and/or age
• OpenIfExists(cfg) — open handler only if tracking file already exists
• All scan functions use optimized directory walking: Readdirnames (cached) for intermediate levels, ReadDir + Info() at leaf level
• Clear and Trim cooperatively update the mmap tracking file if it exists (via OpenIfExists + BeforeRemove), but do not create it
• Empty leaf directories are removed after file deletion (errors ignored for concurrent safety)