Upgrade dependencies: Scala 3.8.4, sbt 1.13.0, sbt-scalajs 1.22.0, sbt-scalajs-crossproject 1.4.0, sbt-pgp 2.3.2, sbt-ci-release 1.12.1

[github-actions]

Upgraded

• Scala 3: 3.8.3 -> 3.8.4
• sbt: 1.12.11 -> 1.13.0 (latest 1.x)
• sbt-scalajs: 1.21.0 -> 1.22.0
• sbt-scalajs-crossproject: 1.3.2 -> 1.4.0
• sbt-pgp: 2.3.1 -> 2.3.2
• sbt-ci-release: 1.11.2 -> 1.12.1
• (transitively via sbt-scalajs) scalajs-test-interface: 1.21.0 -> 1.22.0

Not upgraded

• sbt 2.0.7 (major): skipped — sbt-scalajs and sbt-scalajs-crossproject are not yet published for sbt 2.x. Upgraded to the latest stable 1.x (1.13.0) instead.
• scala-library / scala-reflect major versions (2.12.x -> 2.13.x/3.x): skipped for API compatibility — the project is cross-compiled for 2.12.x, 2.13.x and 3.x.
• Scala 2.12.21 and 2.13.18: already the latest stable versions in their respective lines.

Other changes

• Added sbt-git 2.1.0 explicitly to project/plugins.sbt. sbt-ci-release 1.12.1 dropped its transitive sbt-git dependency, but publish.sbt still relies on GitVersioning (provided by sbt-git), so it must now be declared directly.

Verification

sbt ci-all passes (exit code 0) for all three Scala versions (2.12.21, 2.13.18, 3.8.4).