Simplify project build and stabilize wallpaper history tests

[PrzemyslawKlys]

Summary

• simplify Build/Build-Project.ps1 so it behaves like the OfficeIMO build wrapper and no longer mixes module and tool publishing concerns
• make WallpaperHistory re-evaluate DESKTOPMANAGER_HISTORY_PATH on each access instead of caching the first resolved path
• stabilize WallpaperHistory tests by using isolated temp directories and cleaning them up recursively

Why

PowerBGInfo is moving toward a more standalone packaging story, so DesktopManager build behavior should stay predictable and narrowly scoped. The history-path change also makes the test suite reliable when the environment variable changes during a run.

Validation

• git diff --check
• dotnet build Sources\\DesktopManager.sln
• dotnet test Sources\\DesktopManager.Tests\\DesktopManager.Tests.csproj --no-build --filter WallpaperHistoryTests
• pwsh -NoLogo -NoProfile -File Build\\Build-Project.ps1 -Plan:$true -Build:$false -UpdateVersions:$false

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Do not override publish flags from config

Setting PublishNuget and PublishGitHub to $false by default makes these parameters non-null on every invocation, so the later $null -ne ... checks always pass and Invoke-ProjectBuild is always called with both publish flags forced to false. This silently breaks any workflow that relies on a config file (-ConfigPath) where PublishNuget/PublishGitHub are true, because those config values can no longer take effect unless callers explicitly re-pass :$true on the command line.

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