test(cli): cover remaining extension + decimal render branches

GridRender: vortex.time (I32 ms), vortex.timestamp (I64 ms) and vortex.uuid
(FixedSizeList(U8,16)) extension rendering via the decoder dtype factories.

InspectorRender: GenericArray-backed decimal (single-buffer LE mantissa) and
the bad-shape fallback path through tryDecimal.

Leaves only the DecimalByteParts "null cell" branch uncovered — it needs a
masked byte-parts fixture not worth the weight for one return.

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

Author: dfa1

cli/src/test/java/io/github/dfa1/vortex/cli/tui/GridRenderTest.java

@@ -2,12 +2,18 @@
 
 import io.github.dfa1.vortex.core.DType;
 import io.github.dfa1.vortex.core.PType;
+import io.github.dfa1.vortex.encoding.TimeUnit;
 import io.github.dfa1.vortex.reader.array.Array;
+import io.github.dfa1.vortex.reader.array.ByteArray;
+import io.github.dfa1.vortex.reader.array.FixedSizeListArray;
 import io.github.dfa1.vortex.reader.array.IntArray;
 import io.github.dfa1.vortex.reader.array.LazyConstantDecimalArray;
 import io.github.dfa1.vortex.reader.array.LongArray;
 import io.github.dfa1.vortex.reader.array.MaskedArray;
 import io.github.dfa1.vortex.reader.array.StructArray;
+import io.github.dfa1.vortex.reader.extension.TimeExtensionDecoder;
+import io.github.dfa1.vortex.reader.extension.TimestampExtensionDecoder;
+import io.github.dfa1.vortex.reader.extension.UuidExtensionDecoder;
 import org.junit.jupiter.api.Test;
 
 import java.lang.foreign.Arena;
@@ -80,6 +86,45 @@ void rendersDateExtensionFromIntStorage() {
         }
     }
 
+    @Test
+    void rendersTimeExtensionFromIntStorage() {
+        try (Arena arena = Arena.ofConfined()) {
+            // Given — vortex.time (ms unit) over I32 storage; 0 ms-of-day = midnight
+            DType timeExt = TimeExtensionDecoder.INSTANCE.dtype(TimeUnit.Milliseconds, false);
+            IntArray storage = ArrayFixtures.ints(arena, 0);
+
+            // When / Then
+            assertThat(GridRender.formatCell(storage, 0, timeExt)).isEqualTo("00:00");
+        }
+    }
+
+    @Test
+    void rendersTimestampExtensionFromLongStorage() {
+        try (Arena arena = Arena.ofConfined()) {
+            // Given — vortex.timestamp (ms unit, no tz) over I64 storage; 0 ms = the epoch
+            DType tsExt = TimestampExtensionDecoder.INSTANCE.dtype(TimeUnit.Milliseconds, null, false);
+            LongArray storage = ArrayFixtures.longs(arena, 0L);
+
+            // When / Then
+            assertThat(GridRender.formatCell(storage, 0, tsExt)).isEqualTo("1970-01-01T00:00:00Z");
+        }
+    }
+
+    @Test
+    void rendersUuidExtensionFromFixedSizeListStorage() {
+        try (Arena arena = Arena.ofConfined()) {
+            // Given — vortex.uuid over FixedSizeList(U8,16); all-zero bytes = the nil UUID
+            DType uuidExt = UuidExtensionDecoder.INSTANCE.dtype(false);
+            ByteArray elems = ArrayFixtures.bytes(arena, new byte[16]);
+            FixedSizeListArray storage = new FixedSizeListArray(
+                    new DType.FixedSizeList(new DType.Primitive(PType.U8, false), 16, false), 1, elems);
+
+            // When / Then
+            assertThat(GridRender.formatCell(storage, 0, uuidExt))
+                    .isEqualTo("00000000-0000-0000-0000-000000000000");
+        }
+    }
+
     @Test
     void maskedNullCellRendersEmpty() {
         try (Arena arena = Arena.ofConfined()) {

cli/src/test/java/io/github/dfa1/vortex/cli/tui/InspectorRenderTest.java

@@ -3,6 +3,7 @@
 import io.github.dfa1.vortex.core.DType;
 import io.github.dfa1.vortex.core.PType;
 import io.github.dfa1.vortex.reader.array.Array;
+import io.github.dfa1.vortex.reader.array.GenericArray;
 import io.github.dfa1.vortex.reader.array.IntArray;
 import io.github.dfa1.vortex.reader.array.LazyConstantDecimalArray;
 import io.github.dfa1.vortex.reader.array.MaskedArray;
@@ -11,6 +12,8 @@
 import org.junit.jupiter.api.Test;
 
 import java.lang.foreign.Arena;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
 import java.math.BigDecimal;
 import java.util.List;
 
@@ -57,6 +60,33 @@ void rendersDecimal() {
             assertThat(InspectorRender.formatValue(sut, 0, decimal)).isEqualTo("3.14");
         }
 
+        @Test
+        void rendersGenericArrayDecimal() {
+            try (Arena arena = Arena.ofConfined()) {
+                // Given — GenericArray over an 8-byte LE mantissa 123 at scale 2 → 1.23
+                DType decimal = new DType.Decimal((byte) 10, (byte) 2, false);
+                MemorySegment buf = arena.allocate(8, 8);
+                buf.setAtIndex(ValueLayout.JAVA_LONG, 0, 123L);
+                Array sut = new GenericArray(decimal, 1, buf.asReadOnly());
+
+                // When / Then
+                assertThat(InspectorRender.formatValue(sut, 0, decimal)).isEqualTo("1.23");
+            }
+        }
+
+        @Test
+        void genericArrayDecimalBadShapeRendersFallback() {
+            try (Arena arena = Arena.ofConfined()) {
+                // Given — two buffers: getDecimal rejects the shape with a non-"null cell" error
+                DType decimal = new DType.Decimal((byte) 10, (byte) 2, false);
+                MemorySegment buf = arena.allocate(8, 8);
+                Array sut = new GenericArray(decimal, 1, new MemorySegment[]{buf, buf}, new Array[0]);
+
+                // When / Then — tryDecimal swallows it into the <ClassName dtype> fallback
+                assertThat(InspectorRender.formatValue(sut, 0, decimal)).startsWith("<GenericArray");
+            }
+        }
+
         @Test
         void rendersDateExtension() {
             try (Arena arena = Arena.ofConfined()) {