docs(android): define first-party rules contract

[Windsor Nguyễn (windsornguyen)]

RFC

docs/rfcs/0002-android-rules.md

Determination

The RFC proposes an independently versioned rules/android module. Its public interface uses four Bazel-compatible rules.

Inherited Buck2 code can provide implementation input. Unsupported behavior must return an error. The migration removes the old rule paths.

Evidence

The inherited prelude exposes a different public interface and refers to unavailable Meta infrastructure. Clean Bessemer builds have not verified its documented capabilities.

The RFC remains in discussion. Prototype measurements and clean Linux and macOS builds are acceptance requirements.

Review focus

• Review the initial four-rule interface.
• Review the decision to keep Android rules outside the engine.
• Review the explicit Android SDK and toolchain contract.
• Review whether the validation requirements are sufficient for stable support.

State

• The RFC uses docs/rfcs/template.md.
• Its state is discussion.
• Its discussion field links this pull request.
• Viable alternatives and their costs are documented.
• The validation section defines the requirements for the implemented state.