chore: run .NET workflow on all PRs to main

.github/workflows/dotnet.yml

@@ -1,4 +1,6 @@
 # Build and test the C# solution (server + tests). Targets repo root NeonSprawl.sln.
+# pull_request has no paths filter so this job always runs on PRs to main — add check
+# ".NET / build" under branch protection required status checks (see PR gate workflow comment).
 name: .NET
 
 on:
@@ -10,10 +12,6 @@ on:
       - ".github/workflows/dotnet.yml"
   pull_request:
     branches: [main]
-    paths:
-      - "NeonSprawl.sln"
-      - "server/**"
-      - ".github/workflows/dotnet.yml"
 
 jobs:
   build: