chore: upgrade to .NET 10, migrate to .slnx, bump to 0.4.0-alpha.1

[Shewart]

Summary

First branch of the 0.4 cycle. Bumps every TargetFramework from net9.0 → net10.0, renames the demo folder NET9/ → NET10/, migrates the solution to the new .slnx XML format, removes the EnableStaticWebAssetsCompression=false workaround (the .NET 10 SDK fixed the underlying bug), and bumps the centralized version to 0.4.0-alpha.1.

Single-target net10.0 for simplicity. net9.0 STS reaches EOL this month; net8.0 LTS users can stay on the 0.3.x line until they upgrade. If enterprise demand justifies it later, we can multi-target net8.0;net10.0 in a follow-up before 1.0.

C# 14 modernization (field keyword, partial constructors, extension members, etc.) is intentionally not in this branch — it'll get its own dedicated chore/csharp14-sweep branch later so the diff is reviewable.

Changes

Framework + tooling

• global.json — SDK pin 9.0.100 → 10.0.100
• Directory.Build.props — 0.3.0-rc.1 → 0.4.0-alpha.1
• All 5 first-party .csprojs (Core, Templates, CLI, Components, Tests) — <TargetFramework>net9.0</TargetFramework> → net10.0
• Both demo .csprojs (BlazorInteractiveServer, ShellUI.Preview) — same TFM bump
• Microsoft.AspNetCore.Components.Web package ref 9.0.6 → 10.0.0 (Components)
• Microsoft.AspNetCore.Components.WebAssembly and .DevServer 9.0.0 → 10.0.0 (Preview)
• IntegrationTest1.cs — hardcoded CLI build path bin/Release/net9.0/ → bin/Release/net10.0/

Solution format migration

• ShellUI.sln removed, ShellUI.slnx generated via dotnet sln ShellUI.sln migrate. Cleaner XML, much more diffable, no copy-paste risk:

  <Solution>
    <Configurations>
      <Platform Name="Any CPU" />
      <Platform Name="x64" />
      <Platform Name="x86" />
    </Configurations>
    <Folder Name="/src/">
      <Project Path="src/ShellUI.CLI/ShellUI.CLI.csproj" />
      <Project Path="src/ShellUI.Components/ShellUI.Components.csproj" />
      <Project Path="src/ShellUI.Core/ShellUI.Core.csproj" />
      <Project Path="src/ShellUI.Templates/ShellUI.Templates.csproj" />
    </Folder>
    <Project Path="ShellUI.Tests/ShellUI.Tests.csproj" />
  </Solution>

• All CI workflow dotnet restore|build|test|pack ShellUI.sln invocations updated to ShellUI.slnx

Demo folder rename

• NET9/ → NET10/ (git mv, preserves history per the rename detector). Updated the preview-pages workflow path filters and publish step accordingly.

.NET 10 SDK fixed our workaround

• ShellUI.Components.csproj — <EnableStaticWebAssetsCompression>false</EnableStaticWebAssetsCompression> and the <StaticWebAssetsBuildMode> line are gone. The original comment said "(.NET 10 SDK bug workaround)" — confirmed by dotnet pack working clean without them.

CI workflows

• .github/workflows/ci.yml — dotnet-version: 9.0.x → 10.0.x, .sln → .slnx
• .github/workflows/release.yml — same
• .github/workflows/preview-pages.yml — same + NET9/ShellUI.Preview/** path filter → NET10/ShellUI.Preview/**

Docs

• docs/PROJECT_STATUS.md — prerequisite .NET 9.0 SDK → .NET 10.0 SDK, demo path NET9/BlazorInteractiveServer → NET10/, "Key Decision feat: restructured components and added a few more #4" rewritten to explain why .NET 10 single-target instead of multi-target
• docs/ARCHITECTURE.md — NET9/ → NET10/
• docs/tailwind-setup.md — .NET 9.0 SDK → .NET 10.0 SDK

Verification

• dotnet restore ShellUI.slnx — clean, all packages resolved on .NET 10
• dotnet build ShellUI.slnx -c Release — clean (0 errors, 0 warnings), packages emitted as 0.4.0-alpha.1.nupkg
• dotnet test ShellUI.Tests — 51/51 unit tests passing on net10.0 (skipping the 2 slow CLI integration tests that need scaffolded projects — those will run in the CI smoke step)
• dotnet pack src/ShellUI.Components without the workaround — clean pack succeeds; confirms .NET 10 SDK fixed the bug

Test plan

• CI green on .NET 10 — build, all unit tests, end-to-end smoke (scaffold + shellui init + shellui add chart pie-chart dashboard-02 data-table + dotnet build on a real dotnet new blazor template)
• Local: dotnet new blazor (which now generates a .NET 10 project) + install the prerelease CLI tool from this branch's pack + shellui init + shellui add — confirm it still works end-to-end against the new template
• Local: open ShellUI.slnx in VS 2022 17.10+ and confirm the solution loads correctly
• Verify Blazor-ApexCharts 6.0.2 and System.Linq.Dynamic.Core 1.7.1 work on .NET 10 (they multi-target down to net6.0/netstandard2.0, so they should be fine via roll-forward — the build success above already proves the resolver picks them up)