style(core): clear Sonar/CodeQL smells on A5 new code

- Explicit types where the type is not apparent (IDE0008) in the config DI extensions.
- Use Path.Join instead of Path.Combine in the directory test (avoids the cs/path-combine
  CodeQL alerts; Path.Join never drops earlier segments).
- Hoist the expected names array to a static readonly field (CA1861).

No behavior change; 51 green Core tests.

Author: thiagoluga

src/NeoReports.Core/DependencyInjection/ServiceCollectionExtensions.cs

@@ -63,7 +63,7 @@ public static IServiceCollection AddReportFromConfig(this IServiceCollection ser
         ArgumentNullException.ThrowIfNull(configJson);
 
         services.AddNeoReports();
-        var config = new JsonReportConfigParser().Parse(configJson);
+        ReportConfig config = new JsonReportConfigParser().Parse(configJson);
         services.AddSingleton(config);
         return services;
     }
@@ -91,7 +91,7 @@ public static IServiceCollection AddReportsFromConfigDirectory(
         if (!Directory.Exists(directory))
             throw new DirectoryNotFoundException($"Report config directory not found: {directory}");
 
-        foreach (var file in Directory.EnumerateFiles(directory, searchPattern).OrderBy(f => f, StringComparer.Ordinal))
+        foreach (string file in Directory.EnumerateFiles(directory, searchPattern).OrderBy(f => f, StringComparer.Ordinal))
             services.AddReportFromConfig(File.ReadAllText(file));
 
         return services;

tests/NeoReports.Core.UnitTests/DynamicConfigDiTests.cs

@@ -17,6 +17,8 @@ namespace NeoReports.Core.UnitTests;
 /// </summary>
 public class DynamicConfigDiTests
 {
+    private static readonly string[] AlphaBeta = { "alpha", "beta" };
+
     private static string ConfigNamed(string name) => $$"""
     {
       "name": "{{name}}",
@@ -54,12 +56,12 @@ public async Task Registers_a_config_report_and_runs_it_by_name()
     [Fact]
     public void Loads_every_config_from_a_directory()
     {
-        var directory = Path.Combine(Path.GetTempPath(), "nr-cfg-" + Guid.NewGuid().ToString("N"));
+        var directory = Path.Join(Path.GetTempPath(), "nr-cfg-" + Guid.NewGuid().ToString("N"));
         Directory.CreateDirectory(directory);
         try
         {
-            File.WriteAllText(Path.Combine(directory, "a.json"), ConfigNamed("alpha"));
-            File.WriteAllText(Path.Combine(directory, "b.json"), ConfigNamed("beta"));
+            File.WriteAllText(Path.Join(directory, "a.json"), ConfigNamed("alpha"));
+            File.WriteAllText(Path.Join(directory, "b.json"), ConfigNamed("beta"));
 
             var services = new ServiceCollection();
             services.AddLogging();
@@ -70,7 +72,7 @@ public void Loads_every_config_from_a_directory()
             using var provider = services.BuildServiceProvider();
 
             var registry = provider.GetRequiredService<IReportRegistry>();
-            registry.Names.ShouldBe(new[] { "alpha", "beta" }, ignoreOrder: true);
+            registry.Names.ShouldBe(AlphaBeta, ignoreOrder: true);
         }
         finally
         {