Add column uniqueness validation in ExcelSheetWriter

[Copilot]

ExamplesTable.getRows() returns Map<String, String>, which silently drops data when columns have duplicate names. This adds early validation to fail fast with a clear error message.

Changes

• ExcelSheetWriter.java: Added validateColumnsUniqueness() check in fillData() that throws IllegalArgumentException listing the duplicate column names
• ExcelSheetWriterTests.java: Updated existing test fixtures to use unique columns; added shouldThrowExceptionForDuplicateColumns test

ExamplesTable contains duplicate column names: [name]

Extracted from #6446 per review feedback.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• jitpack.io
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED --add-opens=java.base/java.time=ALL-UNNAMED -Xmx2g -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant (dns block)
• www.puppycrawl.com
  • Triggering command: /opt/hostedtoolcache/CodeQL/2.24.1/x64/codeql/tools/linux64/java/bin/java /opt/hostedtoolcache/CodeQL/2.24.1/x64/codeql/tools/linux64/java/bin/java -jar /opt/hostedtoolcache/CodeQL/2.24.1/x64/codeql/xml/tools/xml-extractor.jar --fileList=/home/REDACTED/work/vividus/.codeql-scratch/dbs/java/working/files-to-index4187075497226290032.list --sourceArchiveDir=/home/REDACTED/work/vividus/.codeql-scratch/dbs/java/src --outputDir=/home/REDACTED/work/vividus/.codeql-scratch/dbs/java/trap/java (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.