[mkurz]

Summary

• Replace the hand-written build and publish workflows with sbt-github-actions generated CI, covering Scala 2.12 and 3.9 on Java 17, 21, and 25 across Ubuntu and macOS.
• Change the plugin group ID to com.github.sbt and update the scripted fixture and installation example.
• Use sbt-dynver instead of a fixed version, preserving the repository's unprefixed release tags.
• Move the build to sbt 2.1.0-M3 and configure the generated publish job for main and release tags.

Verification

• sbt --batch githubWorkflowCheck
• sbt --batch compile and sbt --batch '++ 3.9.0' compile
• sbt --batch test and sbt --batch '++ 3.9.0' test
• sbt --batch scripted and sbt --batch '++ 3.9.0' scripted

No release was run.

[mkurz]

• Add sbt/sbt-slick-codegen VirtusLab/scala-steward-repos#688
• Migrate sbt-slick-codegen to com.github.sbt scala-steward-org/scala-steward#4014