Kotlin Tooling Agp9 Migration

# KMP AGP 9.0 Migration

Android Gradle Plugin 9.0 makes the Android application and library plugins incompatible
with the Kotlin Multiplatform plugin in the same module. This skill guides you through the
migration.

## Step 0: Analyze the Project

Before making any changes, understand the project structure:
1. Read `settings.gradle.kts` (or `.gradle`) to find all modules
2. For each module, read its `build.gradle.kts` to identify which plugins are applied
3. Check if the project uses a Gradle version catalog (`gradle/libs.versions.toml`). If it exists,
   read it for current AGP/Gradle/Kotlin versions. If not, find versions directly in `build.gradle.kts`
   files (typically in the root `buildscript {}` or `plugins {}` block). **Adapt all examples in this
   guide accordingly** — version catalog examples use `alias(libs.plugins.xxx)` while direct usage
   uses `id("plugin.id") version "x.y.z"`
4. Read `gradle/wrapper/gradle-wrapper.properties` for the Gradle version
5. Check `gradle.properties` for any existing workarounds (`android.enableLegacyVariantApi`)
6. Check for `org.jetbrains.kotlin.android` plugin usage — AGP 9.0 has built-in Kotlin and this plugin must be removed
7. Check for `org.jetbrains.kotlin.kapt` plugin usage — incompatible with built-in Kotlin, must migrate to KSP or `com.android.legacy-kapt`
8. Check for third-party plugins that may be incompatible with AGP 9.0 (see "Plugin Compatibility" section below)

If Bash is available, run `scripts/analyze-project.sh` from this skill's directory to get a structured summary.

### Classify Each Module

For each module, determine its type:

| Current plugins                                                          | Migration path                              |
|--------------------------------------------------------------------------|---------------------------------------------|
| `kotlin.multiplatform` + `com.android.library`                           | **Path A** — Library plugin swap            |
| `kotlin.multiplatform` + `com.android.application`                       | **Path B** — Mandatory Android split        |
| `kotlin.multiplatform` with multiple platform entry points in one module | **Path C** — Full restructure (recommended) |
| `com.android.application` or `com.android.library` (no KMP)              | See "Pure Android Tips" below               |

### Determine Scope

- **Path B is mandatory** for any module combining KMP + Android application plugin
- **Path C is recommended** when the project has a monolithic `composeApp` (or similar) module
  containing entry points for multiple platforms (Android, Desktop, Web). This aligns with the
  new JetBrains default project structure where each platform gets its own app module.
- **Ask the user** whether they want Path B only (minimum required) or Path C (recommended full restructure)

## Path A: Library Module Migration

Use this when a module applies `kotlin.multiplatform` + `com.android.library`.

See [references/MIGRATION-LIBRARY.md](references/MIGRATION-LIBRARY.md) for full before/after code.

Summary: