feat(all): add game SDK and harden client login and game rules

- Add costume burst upgrades with durable replay and fix permanent SR equipment gacha.
- Add server game.json rules for optional collaboration UR weapons, with packaging and documentation.
- Add GameNames/GameSdk NuGet tooling, readable types, reobfuscation, complete source/PDB navigation and shared-runtime installation.
- Split plugin responsibilities, prefer typeof/nameof, centralize MSBuild settings and ignore local paths; remove the unused LoginUI test project.
- Fix login recovery and TLS through native platform HTTP and a private game relay; read device region directly from the OS time zone.

Validation: go test ./... -count=1, go vet ./..., plugin Release builds, SDK/runtime self-tests, Roslyn embedded-source navigation, gofmt check and git diff --check.

plugins/GameSdk/Pack.ps1

@@ -0,0 +1,55 @@
+[CmdletBinding()]
+param(
+    [Parameter(Mandatory)] [string]$GameDir,
+    [string]$VersionConfig,
+    [string]$PackageVersion,
+    [string]$OutputDirectory
+)
+$ErrorActionPreference = 'Stop'
+if (-not $VersionConfig) { $VersionConfig = Join-Path $PSScriptRoot '..\..\versions.json' }
+if (-not $OutputDirectory) { $OutputDirectory = Join-Path $PSScriptRoot '..\..\.build\nuget' }
+$repository = [IO.Path]::GetFullPath((Join-Path $PSScriptRoot '..\..'))
+$versions = Get-Content -LiteralPath $VersionConfig -Raw | ConvertFrom-Json
+if (-not $PackageVersion) {
+    [xml]$metadata = Get-Content -LiteralPath (Join-Path $PSScriptRoot '..\PackageMetadata.props') -Raw
+    $PackageVersion = "$($metadata.Project.PropertyGroup.BD2PackageVersion)-game.$($versions.game_version)"
+}
+if ($PackageVersion -notmatch '^\d+\.\d+\.\d+-game\.\d+\.\d+\.\d+(?:\.[A-Za-z0-9-]+)*$') {
+    throw 'PackageVersion must be SemVer with game version, for example 0.2.1-game.2.35.10.'
+}
+if ($PackageVersion -notmatch ('-game\.' + [regex]::Escape([string]$versions.game_version) + '(?:\.|$)')) {
+    throw 'PackageVersion game suffix must match VersionConfig game_version.'
+}
+$OutputDirectory = [IO.Path]::GetFullPath($OutputDirectory)
+$staging = Join-Path $repository ".build\nuget-staging\$PackageVersion"
+$sdk = Join-Path $staging 'sdk'
+$tool = Join-Path $staging 'tool'
+$runtimeObj = Join-Path $staging 'runtime-obj'
+$runtimeBin = Join-Path $staging 'runtime-bin'
+$packageObj = Join-Path $staging 'package-obj'
+$packageBin = Join-Path $staging 'package-bin'
+New-Item -ItemType Directory -Force -Path $OutputDirectory, $staging | Out-Null
+function Invoke-Dotnet([string[]]$Arguments) {
+    & dotnet @Arguments
+    if ($LASTEXITCODE -ne 0) { throw "dotnet failed with exit code $LASTEXITCODE" }
+}
+$toolVersion = $PackageVersion.Split('-')[0]
+Invoke-Dotnet @('publish', (Join-Path $PSScriptRoot 'GameSdk.csproj'), '-c', 'Release', '--nologo', '-o', $tool, "-p:Version=$toolVersion", '-p:UseAppHost=false')
+$assembly = Join-Path $GameDir 'BrownDust II_Data\Managed\Assembly-CSharp.dll'
+$toolDll = Join-Path $tool 'GameSdk.dll'
+Invoke-Dotnet @($toolDll, 'prepare-embedded', $assembly, $sdk, $VersionConfig)
+$table = Join-Path $sdk 'names.json'
+$runtimeProject = Join-Path $PSScriptRoot '..\GameNames\GameNames.csproj'
+Invoke-Dotnet @('pack', $runtimeProject, '-c', 'Release', '--nologo', '-o', $OutputDirectory,
+    "-p:Version=$PackageVersion", "-p:GameNamesTable=$table", "-p:BaseIntermediateOutputPath=$runtimeObj/", "-p:OutputPath=$runtimeBin/")
+Invoke-Dotnet @($toolDll, 'verify-runtime', $table, (Join-Path $runtimeBin 'BD2.GameNames.dll'))
+$packageProject = Join-Path $PSScriptRoot 'Package\BD2.GameSdk.Package.csproj'
+$nugetConfig = Join-Path $staging 'NuGet.Config'
+$escapedSource = [Security.SecurityElement]::Escape($OutputDirectory)
+[IO.File]::WriteAllText($nugetConfig, "<configuration><packageSources><clear/><add key=`"bd2-local`" value=`"$escapedSource`"/><add key=`"nuget.org`" value=`"https://api.nuget.org/v3/index.json`"/></packageSources></configuration>")
+Invoke-Dotnet @('restore', $packageProject, '--configfile', $nugetConfig, "-p:Version=$PackageVersion",
+    '-p:BD2Packaging=true', "-p:BaseIntermediateOutputPath=$packageObj/", "-p:OutputPath=$packageBin/")
+Invoke-Dotnet @('pack', $packageProject, '-c', 'Release', '--no-restore', '--nologo', '-o', $OutputDirectory,
+    "-p:Version=$PackageVersion", "-p:BD2ToolPublishDir=$tool", '-p:BD2Packaging=true',
+    "-p:BaseIntermediateOutputPath=$packageObj/", "-p:OutputPath=$packageBin/")
+Write-Host "Created BD2.GameNames and BD2.GameSdk $PackageVersion in $OutputDirectory"