Returns compiler diagnostics and optional analyzer diagnostics for the loaded C# workspace.
Minimum severity: 'error', 'warning', 'info', or 'hidden'. Default is 'warning'.
Path style: 'absolute' (default) or 'relative' (to solution root).
Optional sort: 'severity', 'filePath', 'id', 'lineNumber', 'projectName'.
Sort order: 'asc' (default) or 'desc'.
compact returns results and actionable state. full adds diagnostic metadata under responseDiagnostics.