Fix compilation warnings after Kotlin 2.4.20 and KSP 2.3.12 upgrade

- Update .idea/kotlinc.xml to Kotlin 2.4.20.
- Remove `-Xannotation-default-target=first-only`: the new annotation
  default target rule is stable in Kotlin 2.4, and disabling it now
  produces a CLI_ARG_DISABLES_STABLE_FEATURE warning.
- Replace deprecated `KSNode.validate()` with
  `validate(enableNewFeatures = false)` to keep the same behavior.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

.idea/kotlinc.xml

@@ -2,6 +2,6 @@
 <project version="4">
   <component name="KotlinJpsPluginSettings">
     <option name="externalSystemId" value="Gradle" />
-    <option name="version" value="2.4.10" />
+    <option name="version" value="2.4.20" />
   </component>
 </project>

build.gradle.kts

@@ -101,10 +101,6 @@ allprojects {
 
             // Uncomment to suppress Compose Kotlin compiler compatibility warning
 //            freeCompilerArgs.addAll(listOf("-P", "plugin:androidx.compose.compiler.plugins.kotlin:suppressKotlinVersionCompatibilityCheck=true"))
-
-            // Fix compilation warning for annotations
-            // See https://youtrack.jetbrains.com/issue/KT-73255/Change-defaulting-rule-for-annotations for more details
-            freeCompilerArgs.add("-Xannotation-default-target=first-only")
         }
     }
 }

codegen/src/main/kotlin/io/element/android/codegen/ContributesNodeProcessor.kt

@@ -53,7 +53,7 @@ class ContributesNodeProcessor(
         val annotatedSymbols = resolver.getSymbolsWithAnnotation(ContributesNode::class.qualifiedName!!)
             .filterIsInstance<KSClassDeclaration>()
 
-        val (validSymbols, invalidSymbols) = annotatedSymbols.partition { it.validate() }
+        val (validSymbols, invalidSymbols) = annotatedSymbols.partition { it.validate(enableNewFeatures = false) }
 
         if (validSymbols.isEmpty()) return invalidSymbols