skill: add Android skills

.agents/skills/agp-9-upgrade/references/ksp-kapt.md

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+When migrating to built-in Kotlin, it is important to consider usage of `kapt`
+and the `org.jetbrains.kotlin.kapt` (also known as the `kotlin("kapt")`) plugin.
+The goal is to migrate as many `kapt` usages to `ksp` as possible.
+
+Follow these steps when migrating `kapt`:
+
+## 1. Remove all references to the `org.jetbrains.kotlin.kapt` plugin
+
+The `org.jetbrains.kotlin.kapt` (also known as `kotlin("kapt")`) plugin is
+incompatible with built-in Kotlin. Remove it when migrating to built-in Kotlin.
+
+## 2. Check each usage of `kapt`
+
+Check each usage of `kapt` to see if it is compatible with `ksp`. To check if a
+dependency is compatible with `ksp`, inspect the dependency's jar. For it to be
+compatible with `ksp`, the jar must have a file,
+`services/com.google.devtools.ksp.processing.SymbolProcessorProvider`. If it
+does not, it is **incompatible** with `ksp`.
+
+For example, the `androidx.room:room-compiler` library is compatible with KSP
+since version 2.3.0-beta02. We can verify this by finding the jar file in the
+Gradle caches directory, which is typically located at
+`~/.gradle/caches/modules-2/files-2.1/` on Linux and Mac. In this specific case,
+the `androidx.room:room-compiler` dependency is located at
+`~/.gradle/caches/modules-2/files-2.1/androidx.room/room-compiler/`.
+
+More generally, you can find a dependency by looking in
+`~/.gradle/caches/modules-2/files-2.1/group-name/artifact-name/`.
+
+## 3. Migrate to KSP where possible
+
+For each usage of `kapt` that is compatible with `ksp`, use `ksp`. The prior
+step explains how to check compatibility.
+
+## 4. Apply legacy-kapt
+
+If a Gradle module has `kapt` dependencies that cannot be migrated to `ksp`
+because they are incompatible (see step 2), then leave that dependency alone and
+apply the `com.android.legacy-kapt` plugin.