fix(core): decode string/bytes scalar values in ArrayStats

Enables utf8 column min/max to appear in zone-map stats and vortex stats output.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfa1

TODO.md

@@ -30,7 +30,6 @@
 
 ## Tooling
 
-- [ ] String min/max in stats — requires utf8 scalar encoding in the proto
 
 ## Large-file support
 

core/src/main/java/io/github/dfa1/vortex/core/ArrayStats.java

@@ -43,6 +43,8 @@ private static Object decodeScalar(ByteBuffer bytes) {
 				case F32_VALUE -> sv.getF32Value();
 				case F64_VALUE -> sv.getF64Value();
 				case BOOL_VALUE -> sv.getBoolValue();
+				case STRING_VALUE -> sv.getStringValue();
+				case BYTES_VALUE -> sv.getBytesValue().toStringUtf8();
 				default -> null;
 			};
 		} catch (com.google.protobuf.InvalidProtocolBufferException e) {