Set IsDirect=true on JAR pom.properties parser output (#128)

JARs are scanned directly, not resolved from a dependency tree, so all
packages found via pom.properties should be marked as direct dependencies.
Mirrors the existing behavior of the pom.xml parser.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: anderruiz

cmd/datadog-sbom-generator/__snapshots__/main_test.snap

@@ -221,6 +221,10 @@ unsupported output format "unknown" - must be one of: json, cyclonedx-1-5
       "version": "1.0.0",
       "purl": "pkg:maven/com.example/my-lib@1.0.0",
       "properties": [
+        {
+          "name": "datadog:is-direct",
+          "value": "true"
+        },
         {
           "name": "datadog:opaque",
           "value": "true"

pkg/lockfile/java/parse-jar-pom-properties.go

@@ -82,6 +82,7 @@ func (e JarPomPropertiesExtractor) Extract(f lockfile.DepFile, context lockfile.
 			PackageManager: jarPomPropertiesPackageManager,
 			Ecosystem:      models.EcosystemMaven,
 			Opaque:         true,
+			IsDirect:       true,
 		})
 	}
 

pkg/lockfile/java/parse-jar-pom-properties_test.go

@@ -159,6 +159,7 @@ func TestParseJarPomProperties_OnePackage(t *testing.T) {
 			PackageManager: models.Maven,
 			Ecosystem:      models.EcosystemMaven,
 			Opaque:         true,
+			IsDirect:       true,
 		},
 	})
 }
@@ -184,13 +185,15 @@ func TestParseJarPomProperties_MultiplePackages(t *testing.T) {
 			PackageManager: models.Maven,
 			Ecosystem:      models.EcosystemMaven,
 			Opaque:         true,
+			IsDirect:       true,
 		},
 		{
 			Name:           "org.other:lib-b",
 			Version:        "3.1.0",
 			PackageManager: models.Maven,
 			Ecosystem:      models.EcosystemMaven,
 			Opaque:         true,
+			IsDirect:       true,
 		},
 	})
 }