dotnet-file-io File I/O patterns for .NET applications. Covers FileStream construction with async flags, RandomAccess API for thread-safe offset-based I/O, File convenience methods, FileSystemWatcher event handling and debouncing, MemoryMappedFile for large files and IPC, path handling security (Combine vs Join), secure temp file creation, cross-platform considerations, IOException hierarchy, and buffer sizing guidance. Out of scope: PipeReader/PipeWriter and network I/O -- see [skill:dotnet-io-pipelines]. Async/await fundamentals -- see [skill:dotnet-csharp-async-patterns]. Span/Memory/Array…