Load ILSpy.sln via a relative path in the DotRush settings

With no configured solution, DotRush only auto-loads when the folder
contains exactly one solution file; this repo has several, so it shows
a picker and writes the chosen absolute path into .vscode/settings.json,
dirtying every fresh clone or worktree. The server resolves configured
entries against the workspace folder it is launched in, so a committed
relative path works everywhere and stops the write-back.

Assisted-by: Claude:claude-fable-5:Claude Code

.vscode/settings.json

@@ -4,4 +4,7 @@
         "ILSpy-tests/**": true
     },
     "dotnet.defaultSolution": "ILSpy.sln",
+    "dotrush.roslyn.projectOrSolutionFiles": [
+        "ILSpy.sln"
+    ],
 }