fix(sonar): array-aware equals/hashCode/toString on ZstdEncodingEncoder records

SonarCloud flagged the private FrameLayout (long[] components) and Frames
(byte[] metadata) records as reliability bugs (java:S6218): a record with array
components gets a default equals/hashCode that compares array identity, not
content. Both are BUG-severity and fail the new-code reliability gate.

Fix by overriding equals/hashCode/toString with Arrays.equals/hashCode/toString
(and Objects for the List/scalar fields) so they consider array content, rather
than suppressing the rule.

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

Author: dfa1

writer/src/main/java/io/github/dfa1/vortex/writer/encode/ZstdEncodingEncoder.java

@@ -14,7 +14,9 @@
 import java.lang.foreign.ValueLayout;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
+import java.util.Objects;
 
 /// Write-only encoder for `vortex.zstd`.
 ///
@@ -145,10 +147,41 @@ private EncodeResult buildNullableResult(
 
     /// Byte spans and value counts of each frame; spans sum to the payload size.
     private record FrameLayout(long[] byteLengths, long[] valueCounts) {
+        @Override
+        public boolean equals(Object o) {
+            return o instanceof FrameLayout(long[] bl, long[] vc)
+                    && Arrays.equals(byteLengths, bl) && Arrays.equals(valueCounts, vc);
+        }
+
+        @Override
+        public int hashCode() {
+            return 31 * Arrays.hashCode(byteLengths) + Arrays.hashCode(valueCounts);
+        }
+
+        @Override
+        public String toString() {
+            return "FrameLayout[byteLengths=" + Arrays.toString(byteLengths)
+                    + ", valueCounts=" + Arrays.toString(valueCounts) + "]";
+        }
     }
 
     /// Compressed frame payloads paired with the encoded `ZstdMetadata` describing them.
     private record Frames(List<MemorySegment> compressed, byte[] metadata) {
+        @Override
+        public boolean equals(Object o) {
+            return o instanceof Frames(List<MemorySegment> c, byte[] m)
+                    && Objects.equals(compressed, c) && Arrays.equals(metadata, m);
+        }
+
+        @Override
+        public int hashCode() {
+            return 31 * Objects.hashCode(compressed) + Arrays.hashCode(metadata);
+        }
+
+        @Override
+        public String toString() {
+            return "Frames[compressed=" + compressed + ", metadata=" + Arrays.toString(metadata) + "]";
+        }
     }
 
     private static int[] frameBufferIndices(int frameCount, int base) {