Merge pull request #192 from erikdarlingdata/fix/rule3-actionable

Fix Rule 3: CouldNotGenerateValidParallelPlan stays Warning

Author: erikdarlingdata

src/PlanViewer.Core/Services/PlanAnalyzer.cs

@@ -141,14 +141,16 @@ private static void AnalyzeStatement(PlanStatement stmt, AnalyzerConfig cfg)
                 _ => stmt.NonParallelPlanReason
             };
 
-            // Only warn (not info) when the user explicitly forced serial execution
-            var isExplicit = stmt.NonParallelPlanReason is "MaxDOPSetToOne" or "QueryHintNoParallelSet";
+            // Warn when the user forced serial or something in the query blocks parallelism.
+            // Info only for passive reasons (cost below threshold, edition limitation).
+            var isActionable = stmt.NonParallelPlanReason is "MaxDOPSetToOne"
+                or "QueryHintNoParallelSet" or "CouldNotGenerateValidParallelPlan";
 
             stmt.PlanWarnings.Add(new PlanWarning
             {
                 WarningType = "Serial Plan",
                 Message = $"Query running serially: {reason}.",
-                Severity = isExplicit ? PlanWarningSeverity.Warning : PlanWarningSeverity.Info
+                Severity = isActionable ? PlanWarningSeverity.Warning : PlanWarningSeverity.Info
             });
         }