Fix filter header colors and add filter diagnostic

- Use blue for "filter" label, green for filter value
- Add diagnostic line showing filter match count before test run

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: rogeralsing

src/Asynkron.TestRunner/LiveDisplay.cs

@@ -146,7 +146,7 @@ public IRenderable Render()
 
             // Build header: show filter if set, otherwise assembly name
             var headerText = !string.IsNullOrEmpty(_filter)
-                ? $"[dim]filter[/] [bold]\"{_filter}\"[/]"
+                ? $"[blue]filter[/] [green]\"{_filter}\"[/]"
                 : _assemblyName ?? "Test Progress";
 
             var panel = new Panel(layout)

src/Asynkron.TestRunner/TestRunner.cs

@@ -52,12 +52,14 @@ public async Task<int> RunTestsAsync(string[] assemblyPaths)
             await using (var discoveryWorker = WorkerProcess.Spawn())
             {
                 var discovered = await discoveryWorker.DiscoverAsync(assemblyPath);
+                var totalDiscovered = discovered.Count;
 
                 // Apply filter if specified
                 if (!string.IsNullOrWhiteSpace(_filter))
                 {
                     var filter = TestFilter.Parse(_filter);
                     discovered = discovered.Where(t => filter.Matches(t.FullyQualifiedName, t.DisplayName)).ToList();
+                    AnsiConsole.MarkupLine($"[dim]Filter applied: {discovered.Count}/{totalDiscovered} tests match[/]");
                 }
 
                 allTests = discovered.Select(t => t.FullyQualifiedName).ToList();