fix: reject malformed history snapshot text

docs/superpowers/plans/2026-07-30-wcs-real-queue-history-replay.md

@@ -10,7 +10,7 @@
 
 **Status (2026-07-31):** Completed and independently reviewed. Final evidence run:
 `outputs/wcs-shadow-history-replay-20260731-0945-af0b52d`; Maven verification:
-354 tests, 0 failures, 0 errors, 0 skipped.
+355 tests, 0 failures, 0 errors, 0 skipped.
 
 ## Global Constraints
 

javaTest/src/main/java/com/ft546/wcs/shadow/history/HistoricalQueueLoader.java

@@ -8,6 +8,10 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
+import java.nio.ByteBuffer;
+import java.nio.charset.CharacterCodingException;
+import java.nio.charset.CharsetDecoder;
+import java.nio.charset.CodingErrorAction;
 import java.nio.file.Path;
 import java.security.MessageDigest;
 import java.net.URLClassLoader;
@@ -82,7 +86,16 @@ public final class HistoricalQueueLoader {
     }
 
     public static void verifySha256(String expected, byte[] bytes) {
-        byte[] canonicalBytes = new String(bytes, StandardCharsets.UTF_8)
+        CharsetDecoder decoder = StandardCharsets.UTF_8.newDecoder()
+                .onMalformedInput(CodingErrorAction.REPORT)
+                .onUnmappableCharacter(CodingErrorAction.REPORT);
+        String text;
+        try {
+            text = decoder.decode(ByteBuffer.wrap(bytes)).toString();
+        } catch (CharacterCodingException ex) {
+            throw new IllegalArgumentException("history snapshot must be valid UTF-8", ex);
+        }
+        byte[] canonicalBytes = text
                 .replace("\r\n", "\n")
                 .replace('\r', '\n')
                 .getBytes(StandardCharsets.UTF_8);

javaTest/src/main/java/com/ft546/wcs/shadow/history/HistoricalReplayReportWriter.java

@@ -10,7 +10,6 @@ import java.nio.file.Path;
 import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.EnumMap;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -50,6 +49,7 @@ public final class HistoricalReplayReportWriter {
         }
         summary.put("vehicles", vehicles);
         summary.put("taskTypes", taskTypes);
+        summary.put("dimensionScope", "REPRESENTATIVE_SAMPLE");
         summary.put("replayableRows", paths.stream().filter(HistoricalPath::isReplayable).count());
         summary.put("qualityIssueRows", paths.stream().filter(p -> !p.getIssues().isEmpty()).count());
         Map<String, Integer> issueCounts = new LinkedHashMap<String, Integer>();

javaTest/src/test/java/com/ft546/wcs/shadow/HistoricalQueueLoaderTest.java

@@ -45,4 +45,13 @@ class HistoricalQueueLoaderTest {
         HistoricalQueueLoader.verifySha256(
                 canonicalSha256, "a\r\nb\r\n".getBytes(StandardCharsets.UTF_8));
     }
+
+    @Test
+    void rejectsMalformedUtf8BeforeCanonicalHashing() {
+        String replacementCharacterSha256 =
+                "83d544ccc223c057d2bf80d3f2a32982c32c3c0db8e2674820da5064783fb097";
+        assertThrows(IllegalArgumentException.class, () ->
+                HistoricalQueueLoader.verifySha256(
+                        replacementCharacterSha256, new byte[]{(byte) 0xc3}));
+    }
 }

javaTest/src/test/java/com/ft546/wcs/shadow/HistoricalReplayAnalyzerTest.java

@@ -92,6 +92,7 @@ class HistoricalReplayAnalyzerTest {
         assertEquals("2026-03-01 10:18:24", summaryJson.path("minCreateDate").asText());
         assertEquals(3, summaryJson.path("vehicles").size());
         assertEquals(3, summaryJson.path("taskTypes").size());
+        assertEquals("REPRESENTATIVE_SAMPLE", summaryJson.path("dimensionScope").asText());
         assertEquals(2, summaryJson.path("qualityIssueCounts").path("UNKNOWN_MAP_SITE").asInt());
         assertEquals(dataset.getRecords().size(),
                 summaryJson.path("replayGrant").asInt()