Use Temurin for setup-java

[skrcode]

Summary

• replace the deprecated adopt distribution with temurin in the test and deploy workflows
• preserve Java 21, x64, Maven caching, and the pinned setup-java action version

Context

This follows the maintainer request on #707 to apply the repair as an independent commit against main, where Renovate cannot overwrite it. setup-java v5 deprecates adopt in favor of temurin, and setup-java v6 removes the legacy alias. Once this lands, Renovate can rebase #705 onto the durable fix.

Verification

• mvn -B -ntp clean verify with JDK 21 — BUILD SUCCESS across all 9 reactor modules
• parsed all 3 repository workflow YAML files
• git diff --check

AI assistance

• JAIPilot skills used: jaipilot-maintainer-intent, jaipilot-fast-execution, and jaipilot-review-diff
• JAIPilot: https://github.com/JAIPilot/jaipilot
• Host model identifier: not exposed by host
• Reasoning effort: not exposed by host
• Execution/service mode: local execution; JAIPilot Remote was not used