[1.x] Fix #9190: avoid leaving partial jar after interrupted package (#9196)

Resource and JAR atomicity is pushed down into sbt/io 1.12.0-SNAPSHOT
(IO.copyFile, IO.transfer, IO.jar/zip stage to a sibling temp file and
atomic-move into place). Bump sbt's io dependency to consume that.

In Package.makeJar, stop deleting the existing JAR before calling IO.jar.
Atomic IO.jar replaces the destination only after the staged JAR is
complete, so deleting up front would just destroy the last good artifact
on interrupt without changing the failure mode.

Generated-by: Codex (gpt-5.5) and Claude Sonnet 4.6

main-actions/src/main/scala/sbt/Package.scala

@@ -221,9 +221,7 @@ object Package {
     val path = jar.getAbsolutePath
     log.debug("Packaging " + path + " ...")
     if (jar.exists)
-      if (jar.isFile)
-        IO.delete(jar)
-      else
+      if (!jar.isFile)
         sys.error(path + " exists, but is not a regular file")
     log.debug(sourcesDebugString(sources))
     IO.jar(sources, jar, manifest, time)

project/Dependencies.scala

@@ -13,7 +13,7 @@ object Dependencies {
     sys.env.get("BUILD_VERSION") orElse sys.props.get("sbt.build.version")
 
   // sbt modules
-  private val ioVersion = nightlyVersion.getOrElse("1.10.5")
+  private val ioVersion = nightlyVersion.getOrElse("1.12.0")
   private val lmVersion =
     sys.props.get("sbt.build.lm.version").orElse(nightlyVersion).getOrElse("1.12.2")
   val zincVersion = nightlyVersion.getOrElse("1.12.0")