Initial commit: terminal Minesweeper in C# for .NET 10

A playable console Minesweeper (arrow keys, chording, flags, question marks,
pause, difficulty presets) plus a deduction-and-guess solver that can play the
game headlessly. Game logic lives in src/Minesweeper/Game and has no console
dependencies, so it is covered by 65 unit tests.

Includes publishing helpers for self-contained, trimmed single-file binaries
(publish.sh) and an .editorconfig that the sources conform to: UTF-8 BOM and
4-space indents for C#, 2-space indents for project files, LF endings and
2-space indents for shell scripts, System-first usings, no redundant `this.`,
and s_/ _ prefixed private static and instance fields.

tests/Minesweeper.Tests/Minesweeper.Tests.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="../../src/Minesweeper/Minesweeper.csproj" />
+  </ItemGroup>
+
+</Project>