Meta Spatial SDK: the Android lane onto Horizon OS

Spatial SDK lets an Android team ship an immersive app in Kotlin: Android Studio, Gradle, Jetpack Compose, the libraries they already use — with OpenXR underneath and an ECS data model on top. A panel in the scene is a real Android view, not a texture someone drew to look like one.

For a whole-product roadmap or stage audit, use quest-lifecycle; a single technical task stays with this owner. If absent, identify the current stage, its evidence and the next prerequisite inline.

Read references/hybrid-activities.md when mixing panel and immersive activities: exclusive/cooperative modes, state ownership and transition tests.

Step 0 — is this the right lane?