chore(workspace): adopt UPM package submodules

.gitignore

@@ -7,8 +7,6 @@
 /[Ll]ibrary/
 /[Tt]emp/
 /[Oo]bj/
-/DotNet/**/[Bb]in/
-/DotNet/**/[Oo]bj/
 /TestResults/
 /[Bb]uild/
 /[Bb]uilds/
@@ -59,16 +57,6 @@ ExportedObj/
 *.opendb
 *.VC.db
 
-# Tracked source project for rebuilding ShrinkModFramework external DLL fixtures.
-!Tools/ShrinkModFixtureBuilder/ShrinkModFixtureBuilder.csproj
-Tools/ShrinkModFixtureBuilder/bin/
-Tools/ShrinkModFixtureBuilder/obj/
-
-# Tracked standalone .NET projects for ShrinkEventBus runtime and generator validation.
-!DotNet/ShrinkEventBus.Core/ShrinkEventBus.Core.csproj
-!DotNet/ShrinkEventBus.Generator/ShrinkEventBus.Generator.csproj
-!DotNet/ShrinkEventBus.Smoke/ShrinkEventBus.Smoke.csproj
-
 # Unity3D generated meta files
 *.pidb.meta
 *.pdb.meta