[He-Pin]

Motivation

Align the independent sbt examples with Apache Pekko core's formatter tooling while keeping each example self-contained.

Modification

• Configure all 17 independent sbt builds with Scalafmt 3.11.5 and sbt-scalafmt 2.6.2.
• Provide applyCodeStyle and checkCodeStyle aliases and document their use.
• Configure sbt-java-formatter 0.14.0 in the 4 builds containing Java sources, using the Java 17 formatter without import sorting.
• Include MultiJvm Scala sources in the five relevant builds. Preserve the Scala 3 dialect in the Scala 3 samples.
• Preserve Scala 2 syntax where applicable by using the Scala 2 dialect and disabling Scala 3 syntax rewrites; do not change compiler language modes.
• Apply the corresponding formatter output without changing snippet identifiers or runtime logic. Maven-only examples are unchanged.

Result

The one-time formatter output touches 29 Java and 25 Scala source files; the remaining changes are tooling/configuration and documentation.

The examples expose consistent, self-contained formatting commands instead of relying on a checkout of the core repository.

Tests

• JDK 17: sbt applyCodeStyle checkCodeStyle passed in all 17 independent builds, including all five MultiJvm configurations and the four Java-enabled builds.
• pekko-sample-cluster-java: compile, MultiJvm / compile, and test passed. The distributed MultiJvm suite was compiled, not executed.
• docs-gen: pekko-sample-cluster-java / paradox passed with the process-local JVM flag --add-opens=java.base/java.lang=ALL-UNNAMED, required by its existing Parboiled version on JDK 17. Without that compatibility flag it fails during parser initialization.
• Verified that documentation snippet identifiers/pairs were preserved. Java token comparison preserves runtime code after accounting for formatter removal of unused imports, modifier ordering, and equivalent adjacent string-literal wrapping.
• git diff --check passed. No CI inspection/monitoring. Other samples' full test suites were not run; all formatter workflows were exercised.
• No new runtime source files were added. headerCreateAll was attempted in the representative sample but is unavailable (Not a valid key); no unrelated header plugin was introduced.

References

Refs #206: separate existing Scalafix OrganizeImports work; this PR does not add that tooling.

Core reference: apache/pekko 6049edf9.