Android native regressions

From the repository root:

apps/mobile/modules/t3-review-diff/tests/run-android.sh

Requires JDK 17+ (JAVA_HOME) and Gradle on PATH. Tested with JDK 17 and Gradle 9.4.1. To use another installed Gradle or a wrapper, set GRADLE=/absolute/path/to/gradle before the command. The runner resolves its own location, so it also works from other directories. Gradle test options are forwarded, for example --tests '*ReviewDiffViewportTest' --rerun-tasks.

This standalone JVM build registers the viewport and geometry regressions and the module's existing android/src/test layout suite with Gradle's test task. It compiles the module's actual Android view, drawing, and layout sources. Pinned Maven dependencies supply Kotlin, Robolectric, Android API 35, and AndroidX test classes. The first run requires access to Maven Central and Google Maven, including Robolectric's runtime SDK download. No local Android SDK, Expo prebuild, device, temporary checkout, or pre-extracted jars are needed. Generated files stay in ignored build/ and .gradle/ directories; the HTML report is build/reports/tests/test/index.html.

The three files under stubs/expo/modules/kotlin/ replace only Expo's context, view base class, and event dispatcher. Events go to a per-test context instead of a React Native bridge. This checks reset/decode ordering, stale-row removal, and viewport publication in the real view, but does not validate Expo registration, JS event delivery, native libraries, or device rendering. These stubs are exclusive to this standalone build and must not be added to the production Android source set. Geometry regressions bound sticky-header row reads, check lazy ASCII layout retention and syntax invalidation, and compare ASCII widths against Android paint metrics. Native shaping tests cover tabs, Unicode clusters, and styled word-diff spans.