fix: use manual Gradle build for CodeQL java-kotlin analysis

[svarlamov]

Summary

• switch the CodeQL java-kotlin matrix entry from autobuild to manual
• set up Java 21 and Gradle before the CodeQL manual build step
• run agent-support/intellij/./gradlew classes so CodeQL analyzes the actual IntelliJ plugin sources

Verification

• cd agent-support/intellij && ./gradlew classes
• inspected the failing CodeQL job log to confirm autobuild failed during build-command detection

---

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

---

Test Runner seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[svarlamov]

• fix: use manual Gradle build for CodeQL java-kotlin analysis #965 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.