Release 4.2.0

- PUBLISH_VERSION 4.1.1 -> 4.2.0
- CHANGELOG: promote [Unreleased] -> [4.2.0] (2026-06-08) + compare link
- README: bump install snippets to 4.2.0

Adds the Android target for tree-structure and tree-structure-compose,
the default TreeNodeRow composable + LazyTree(label=...) overload, and a
runnable Android sample. All additive, no breaking changes.

README.md

@@ -30,14 +30,14 @@ Gradle (Kotlin DSL):
 ```kotlin
 // commonMain for KMP projects, or any sourceSet/module where you need it
 dependencies {
-    implementation("com.github.adriankuta:tree-structure:4.1.1") // latest version is on the badge above
+    implementation("com.github.adriankuta:tree-structure:4.2.0") // latest version is on the badge above
 }
 ```
 
 Gradle (Groovy):
 ```groovy
 dependencies {
-    implementation "com.github.adriankuta:tree-structure:4.1.1"
+    implementation "com.github.adriankuta:tree-structure:4.2.0"
 }
 ```
 
@@ -46,7 +46,7 @@ Maven:
 <dependency>
   <groupId>com.github.adriankuta</groupId>
   <artifactId>tree-structure</artifactId>
-  <version>4.1.1</version>
+  <version>4.2.0</version>
 </dependency>
 ```
 
@@ -160,7 +160,7 @@ that depends on the core.
 `@Serializable` directly. Convert to and from the acyclic `TreeNodeDto` instead.
 
 ```kotlin
-implementation("com.github.adriankuta:tree-structure-serialization:4.1.1")
+implementation("com.github.adriankuta:tree-structure-serialization:4.2.0")
 ```
 ```kotlin
 val json = Json.encodeToString(root.toDto())
@@ -172,7 +172,7 @@ val restored = Json.decodeFromString<TreeNodeDto<String>>(json).toTreeNode()
 Traverse a tree as a cold `Flow`, which is handy inside coroutine and `ViewModel` pipelines.
 
 ```kotlin
-implementation("com.github.adriankuta:tree-structure-coroutines:4.1.1")
+implementation("com.github.adriankuta:tree-structure-coroutines:4.2.0")
 ```
 ```kotlin
 root.preOrderFlow().collect { println(it.value) }
@@ -185,7 +185,7 @@ A `LazyTree` composable for Compose Multiplatform (JVM/desktop, Android, iOS, Wa
 nodes are composed.
 
 ```kotlin
-implementation("com.github.adriankuta:tree-structure-compose:4.1.1")
+implementation("com.github.adriankuta:tree-structure-compose:4.2.0")
 ```
 
 For the common case, the no-content overload renders each node with the built-in `TreeNodeRow`
@@ -217,7 +217,7 @@ subtrees are reused, so updates are cheap and old roots stay valid. Backed by
 `kotlinx.collections.immutable`.
 
 ```kotlin
-implementation("com.github.adriankuta:tree-structure-immutable:4.1.1")
+implementation("com.github.adriankuta:tree-structure-immutable:4.2.0")
 ```
 ```kotlin
 val root = ImmutableTreeNode("World").addChild(ImmutableTreeNode("Europe"))