feat: Adds Build Tool for Publishing/Setup (#2392)

## Summary

Replaces the basic `publish.cmd`/`publish.sh` scripts with an interactive **BuildTool** — a C# console app using [Spectre.Console](https://spectreconsole.net/) that guides users through publishing, prerequisite checking, and cross-compilation.

### Why
The community found the existing publish scripts unhelpful for newcomers. They worked but didn't walk users through the process, didn't check prerequisites, and provided no feedback when things went wrong.

### What's New

**Interactive BuildTool** (`Projects/BuildTool/`)
- NativeAOT-compiled C# console app with true-color ASCII logo and ModernUO brand gold/silver palette
- Guided publish wizard with step-by-step back navigation (Ctrl+C or menu "Back" to go to previous step)
- Prerequisite checking: .NET SDK version, VC++ Redistributable (Windows), native libraries (Linux/macOS)
- .NET SDK auto-install offer via Microsoft's official install scripts
- Platform detection: Windows 10 vs 11 (build number), macOS codenames, Linux distro + kernel version
- Cross-compilation support: skips native library checks, shows target prerequisites after build
- Non-interactive mode for CI: `--config Release --skip-prereqs`
- Backward-compatible positional args: `publish.cmd release win x64` still works

**Shell Wrappers** (`publish.cmd`, `publish.ps1`, `publish.sh`)
- Try native BuildTool binary first (downloaded from GitHub Releases)
- Fall back to `dotnet run --project Projects/BuildTool` if unavailable
- SDK bootstrapping: offer to install .NET if not found

**CI/CD Updates**
- Build/test workflows target `Projects/Application/Application.csproj` instead of the solution (excludes BuildTool and test projects from publish)
- New `build-tool-release.yml` workflow builds NativeAOT binaries for win-x64, win-arm64, osx-arm64, linux-x64, linux-arm64
- Minimum SDK bumped to 10.0.201 (required for Serialization Generator 2.14.3 / Roslyn 5.3.0)

**Other Changes**
- Solution converted from `.sln` to `.slnx`
- Updated README with interactive mode instructions and deployment guidance

## Screenshots

<img width="320" height="378" alt="image" src="https://github.com/user-attachments/assets/83c057c5-3992-4dbd-99fa-0e3c24ef6428" />

<img width="749" height="554" alt="image" src="https://github.com/user-attachments/assets/e4ee4d6f-71d4-47f9-86b6-8fd1ca3c3e7a" />

README.md

@@ -56,14 +56,25 @@ ModernUO [![Discord](https://img.shields.io/discord/751317910504603701?logo=disc
 - Open `ModernUO.sln` to start developing
 
 ## Building/Publishing
-- Run `./publish.cmd [release|debug (default: release)] [os] [arch (default: x64)]`
-  - `os` - [Supported operating systems](https://github.com/dotnet/core/blob/main/release-notes/10.0/supported-os.md)
-    - `win` - [Windows](https://learn.microsoft.com/en-us/dotnet/core/install/windows)
-    - `osx` - [MacOS](https://learn.microsoft.com/en-us/dotnet/core/install/macos)
-    - `linux` - [Linux](https://learn.microsoft.com/en-us/dotnet/core/install/linux)
-  - `arch`
-    - `x64` - Intel/AMD 64-bit
-    - `arm64` - ARM 64-bit (Windows not supported)
+
+#### Interactive Mode (Recommended for new users)
+Run `./publish.cmd` (Windows) or `./publish.sh` (Linux/macOS) with no arguments to launch the guided build tool. It will:
+- Check prerequisites (.NET SDK, native libraries)
+- Walk you through configuration and platform selection
+- Build and publish the server to the `Distribution` directory
+- Show deployment instructions for cross-compiled builds
+
+#### Command Line
+```shell
+./publish.cmd [release|debug] [os] [arch]
+```
+- `os` - [Supported operating systems](https://github.com/dotnet/core/blob/main/release-notes/10.0/supported-os.md)
+  - `win` - [Windows](https://learn.microsoft.com/en-us/dotnet/core/install/windows)
+  - `osx` - [macOS](https://learn.microsoft.com/en-us/dotnet/core/install/macos)
+  - `linux` - [Linux](https://learn.microsoft.com/en-us/dotnet/core/install/linux)
+- `arch`
+  - `x64` - Intel/AMD 64-bit
+  - `arm64` - ARM 64-bit
 
 ## Linux Prerequisites
 ### Fedora, CentOS, RHEL, etc
@@ -87,7 +98,9 @@ brew install icu4c libdeflate zstd argon2
 
 ## Running the Server
 - Follow the [publish](https://github.com/modernuo/ModernUO#buildingpublishing) instructions
+- The `Distribution` directory is portable — copy it to your production server for deployment
 - Run `ModernUO.exe` or `dotnet ModernUO.dll` from the `Distribution` directory
+- On first run, the server will prompt you to configure game data file locations
 
 ## Troubleshooting / FAQ
 - See [FAQ](./FAQ.md)