create PackageManifest.kt and get test working

gui/build.gradle.kts

@@ -0,0 +1,20 @@
+plugins {
+    kotlin("jvm")
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation(project(":api"))
+    implementation(project(":cli"))
+    testImplementation(kotlin("test"))
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
+kotlin {
+    jvmToolchain(21)
+}