test(reader): cover VortexHttpReader.open(uri, registry) overload

The CLIENT -> DEFAULT_HTTP_CLIENT rename marked the two-arg open()
delegation as new code; it was the only uncovered new line, dragging
SonarCloud new-code coverage to 50% and failing the quality gate. The
one- and three-arg overloads were already covered (IT + mock-client
unit tests); this adds an IT for the two-arg overload.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

reader/src/test/java/io/github/dfa1/vortex/reader/VortexHttpReaderIT.java

@@ -61,6 +61,21 @@ void open_remoteFile_layoutRowCountIsPositive() throws Exception {
         }
     }
 
+    @Test
+    void open_withCustomRegistry_parsesMetadata() throws Exception {
+        // Given the two-arg overload: caller supplies a registry, default shared HttpClient.
+        // The three-arg overload is exercised by the mock-client unit tests, but this
+        // delegating overload was otherwise untested.
+
+        // When
+        try (var sut = VortexHttpReader.open(FOR_ARRAY, ReadRegistry.loadAll())) {
+
+            // Then
+            assertThat(sut.version()).isEqualTo(1);
+            assertThat(sut.dtype()).isNotNull();
+        }
+    }
+
     @Test
     void scan_forVortex_decodesAllRows() throws Exception {
         // Given