Complete Java and Kotlin CI coverage

[kserrec]

Summary

• add the Java expected-output baseline captured from the successful execution in PR Java #29
• make the Java test runnable from any working directory and replace the stale manual Oracle installation guide
• add a Kotlin test that compiles to a temporary runnable jar, executes it, and removes the artifact
• add the Kotlin expected-output baseline captured from an actual Kotlin 2.4.10 and Java 21 run
• document the Kotlin build and test workflow
• complete Milestone 1 Step 5 and remove the finished Java README housekeeping item

The existing Kotlin implementation compiled and produced the correct results unchanged. GitHub ubuntu-latest already includes Kotlin 2.4.10 and Java 17, so this adds no package installer or third-party setup action.

Verification

• Java test executed in Eclipse Temurin Java 21
• Kotlin test executed with the checksum-verified official Kotlin 2.4.10 compiler and Eclipse Temurin Java 21
• both focused outputs matched their expected-output files byte-for-byte
• shell syntax and git diff checks passed
• root harness result: 9 passed, 0 failed, 8 locally unavailable toolchains skipped, 0 pending

GitHub Actions is the final verification against the runner-provided Java and Kotlin toolchains.