Migrate KMP Android modules before AGP 10

[alexstyl]

Deadline

• Internal completion deadline: October 31, 2026
• AGP 10 release window: late 2026
• Google currently describes this as an estimate and has not published an exact release date: https://developer.android.com/build/releases/gradle-plugin-roadmap

Why

PR #502 upgrades the project to AGP 9.1.1 but temporarily retains the legacy AGP/KMP integration with:

android.builtInKotlin=false
android.newDsl=false

AGP 10 removes these compatibility opt-outs. The project must migrate before upgrading to AGP 10.

Scope

• Migrate KMP library modules from com.android.library to com.android.kotlin.multiplatform.library.
• Replace the current androidTarget and top-level android configuration with the Android-KMP DSL.
• Preserve Android instrumented-test coverage and configure device tests explicitly where required.
• Decide and document how the new single-variant Android-KMP publishing model replaces the current debug/release publications.
• Move Android application entry points out of KMP modules into standalone Android app modules where required.
• Remove android.builtInKotlin=false and android.newDsl=false.

Acceptance criteria

• No module combines org.jetbrains.kotlin.multiplatform with com.android.library or com.android.application.
• The two AGP compatibility flags are removed.
• Existing Maven coordinates and intended Android publications are preserved or intentionally migrated.
• jvmTest and spotlessCheck pass.
• All Android demo applications assemble.
• All Android connected-test modules pass.
• Full Nightly Checks complete without AGP/KMP compatibility warnings or failures attributable to the migration.

Context

• Compatibility bridge: Fix Android builds with Compose Multiplatform 1.12 #502
• Android-KMP plugin migration guide: https://developer.android.com/kotlin/multiplatform/plugin