migrate-dotnet9-to-dotnet10

# .NET 9 → .NET 10 Migration Migrate a .NET 9 project or solution to .NET 10, systematically resolving all breaking changes. The outcome is a project targeting `net10.0` that builds cleanly, passes tests, and accounts for every behavioral, source-incompatible, and binary-incompatible change introduced in the .NET 10 release. ## When to Use - Upgrading `TargetFramework` from `net9.0` to `net10.0` - Resolving build errors or new warnings after updating the .NET 10 SDK - Adapting to behavioral changes in .NET 10 runtime, ASP.NET Core 10, or EF Core 10 - Updating CI/CD pipelines, Dockerfiles, or deployment scripts for .NET 10 - Migrating from the community `System.Linq.Async` package to the built-in `System.Linq.AsyncEnumerable` ## When Not to Use - The project already targets `net10.0` and builds cleanly — migration is done - Upgrading from .NET 8 or earlier — use the `migrate-dotnet8-to-dotnet9` skill first to reach `net9.0`, then return to this skill for the `net9.0` → `net10.0` migration - Migrating from .NET Framework — that is a separate, larger effort - Greenfield projects that start on .NET 10 (no migration needed) ## Inputs | Input | Required | Description | |-------|----------|-------------| | Project or solution path | Yes | The `.csproj`, `.sln`, or `.slnx` entry point to migrate | | Build command | No | How to build (e.g., `dotnet build`, a repo build script). Auto-detect if not provided | | Test command | No | How to run tests (e.g., `dotnet test`). Auto-dete...