Fix Kotest project config discovery for undertest-kotest

Set kotest.framework.config.fqn system property so Kotest 6 can find
KotestProjectConfig, enabling SelfieExtension to initialize properly.
Without this, all tests failed with "SelfieExtension wasn't added to
the AbstractProjectConfig".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sksamuel

jvm/settings.gradle

@@ -29,6 +29,8 @@ plugins {
   id 'org.jetbrains.kotlin.multiplatform' version '2.2.20' apply false
   // https://github.com/adamko-dev/dokkatoo/releases
   id 'dev.adamko.dokkatoo-html' version '2.4.0' apply false
+  // https://plugins.gradle.org/plugin/io.kotest
+  id 'io.kotest' version '6.1.1' apply false
 }
 
 blowdryerSetup {

jvm/undertest-junit5-kotest/harness/gradle.properties

@@ -9,4 +9,4 @@ ver_JUNIT_PIONEER=2.2.0
 ver_OKIO=3.7.0
 ver_KOTLIN_TEST=1.9.22
 ver_KOTLIN_SERIALIZATION=1.6.3
-ver_KOTEST=6.1.0
+ver_KOTEST=6.1.1

jvm/undertest-junit5-kotest/harness/settings.gradle

@@ -29,6 +29,8 @@ plugins {
     id 'org.jetbrains.kotlin.multiplatform' version '2.2.20' apply false
     // https://github.com/adamko-dev/dokkatoo/releases
     id 'dev.adamko.dokkatoo-html' version '2.4.0' apply false
+    // https://plugins.gradle.org/plugin/io.kotest
+    id 'io.kotest' version '6.1.1' apply false
 }
 
 blowdryerSetup {

jvm/undertest-kotest/build.gradle

@@ -1,6 +1,7 @@
 plugins {
   id 'org.jetbrains.kotlin.multiplatform'
   id 'com.diffplug.spotless'
+  id 'io.kotest'
 }
 repositories {
   mavenCentral()
@@ -46,6 +47,7 @@ tasks.named('jvmTest').configure {
   testLogging.showStandardStreams = true
   // the snapshots are both output and input, for this harness best if the test just always runs
   outputs.upToDateWhen { false }
+  systemProperty "kotest.framework.config.fqn", "kotest.KotestProjectConfig"
   // defaults to 'write'
   String SELFIE = findProperty('selfie')
   if (SELFIE != null) {