IAsyncEnumerable with yield in C#: sample moved to async-csharp/IAsyncEnumerableWithYield on .NET 10

[vladimir-pecanac-main]

Sample for https://code-maze.com/csharp-async-enumerable-yield/ ("IAsyncEnumerable with yield in C#").

The sample used to live in the standalone repository CodeMazeBlog/async-enumerable-yield-csharp (net6.0, Startup.cs, Swashbuckle 5.6.3, no tests). This PR moves it into async-csharp/IAsyncEnumerableWithYield, next to CancellationTokensIAsyncEnumerable. The old repository is not changed by this PR.

What is in the folder:

• TaskOfIEnumerable, SyncYield and IAsyncEnumerableWithYield: the three console programs the article walks through (Task<IEnumerable>, synchronous yield return, async IAsyncEnumerable with await foreach), each a net10.0 top-level Program.cs that matches the article's code.
• IAsyncEnumerableWithYieldApi: net10.0 Web API on minimal hosting (one Program.cs, no Startup class, no Swashbuckle). ValuesController, a minimal API endpoint at /items, and an EF Core ItemsController that streams rows with AsNoTracking().AsAsyncEnumerable() over SQLite (created and seeded at startup, so nothing external is needed). The launch profile keeps https://localhost:5001 and http://localhost:5000.
• Tests (MSTest): /api/values and /items deliver their first item before the last, the EF Core query runs no command until it is enumerated, and /api/items returns every row. No test needs a live resource.

Packages (NuGet re-queried 2026-10-11, latest listed stable):

• Microsoft.EntityFrameworkCore.Sqlite 10.0.12
• Microsoft.AspNetCore.Mvc.Testing 10.0.12
• Microsoft.NET.Test.Sdk 18.10.1
• MSTest.TestAdapter 4.5.1
• MSTest.TestFramework 4.5.1
• coverlet.collector 10.1.0

Checked locally on SDK 10.0.302, runtime 10.0.10: dotnet build -c Release 0 warnings, 0 errors; dotnet test 4 passed, 0 failed; dotnet list package --vulnerable --include-transitive reports no vulnerable packages in any of the five projects.