[AI-4146] Downgrade to sbt 1.12.8 for Metals/Bloop compatibility (russwyte#40)

* [AI-4145] Add fork-friendly GitHub Packages publishing support

Add env-var-driven publishing so forks can publish to their own GitHub
Packages repository without modifying build files. Controlled by repo
variables: PUBLISH_PACKAGES_REPO, PUBLISH_ORG, PUBLISH_ORG_NAME.
Includes a publish workflow that is a no-op when variables are unset.

* [AI-4146] Downgrade to sbt 1.12.8 for Metals/Bloop compatibility

- Downgrade from sbt 2.0.0-RC10 to 1.12.8 (RC has cross-version conflicts
  with sbt-bloop that break Metals)
- Add jsoniter-scala-core_2.13 exclusion to fix remaining conflict
- Enable semanticdbEnabled for Metals support
- Minor scalafmt formatting adjustments

Author: russwyte

build.sbt

@@ -1,6 +1,7 @@
-
 val scala3Version = "3.7.4"
 val zioVersion    = "2.1.24"
+// lets enable semanticdb
+ThisBuild / semanticdbEnabled := true
 
 ThisBuild / dependencyOverrides += "org.scalameta" % "semanticdb-scalac_2.12.21" % "4.14.4"
 ThisBuild / scalaVersion                          := scala3Version
@@ -23,24 +24,28 @@ ThisBuild / developers := List(
     url = url("https://github.com/russwyte"),
   )
 )
-ThisBuild / versionScheme          := Some("early-semver")
+ThisBuild / versionScheme := Some("early-semver")
 
 // --- Fork publishing support (GitHub Packages) ---
 // Forks set PUBLISH_PACKAGES_REPO and GITHUB_TOKEN in CI to publish to their own GitHub Packages.
 // Optionally set PUBLISH_ORG and PUBLISH_ORG_NAME to change the Maven group ID.
 val githubPackagesRepo: Option[MavenRepository] =
   sys.env.get("PUBLISH_PACKAGES_REPO").map("GitHub Packages" at _)
 
-ThisBuild / credentials ++= sys.env.get("GITHUB_TOKEN").map { token =>
-  Credentials("GitHub Package Registry", "maven.pkg.github.com", "_", token)
-}.toSeq
+ThisBuild / credentials ++= sys.env
+  .get("GITHUB_TOKEN")
+  .map { token =>
+    Credentials("GitHub Package Registry", "maven.pkg.github.com", "_", token)
+  }
+  .toSeq
 
 ThisBuild / resolvers ++= githubPackagesRepo.toSeq
 
 // PGP signing: only when publishing to Maven Central (forks targeting GitHub Packages won't have the key)
-githubPackagesRepo match
+githubPackagesRepo match {
   case None    => usePgpKeyHex("2F64727A87F1BCF42FD307DD8582C4F16659A7D6")
   case Some(_) => Seq.empty
+}
 
 ThisBuild / libraryDependencies ++= Seq(
   "dev.zio" %% "zio"                      % zioVersion % "provided",

project/build.properties

@@ -1 +1 @@
-sbt.version=2.0.0-RC10
+sbt.version=1.12.8

project/plugins.sbt

@@ -12,6 +12,7 @@ addSbtPlugin("org.scoverage" % "sbt-scoverage" % "2.4.4")
 excludeDependencies ++= Seq(
   ExclusionRule("org.scala-lang.modules", "scala-xml_2.13"),
   ExclusionRule("org.scala-lang.modules", "scala-collection-compat_2.13"),
+  ExclusionRule("com.github.plokhotnyuk.jsoniter-scala", "jsoniter-scala-core_2.13"),
 )
 
 // val overrideSemanticDbVersion = "4.14.5"