feat(android): Kotlin/Jetpack Compose backend

[tiensonqin]

Summary

Adds a Kotlin / Jetpack Compose backend that renders the LUI wire protocol on Android — a full port of the Apple backend's coverage, plus the KotlinHost wiring needed for the OCaml side to target it.

Note on diff size: this branch is built on top of devin/remove-flutter (per coordinator sequencing); the Flutter-deletion diff shows here until #134 lands.

Kotlin library (platform/android/lui, package dev.lui, ~4.9k lines):

• LuiWire — patch-batch JSON parser (kotlinx.serialization) covering all ops
• LuiStore / LuiRetainedTree — retained node store; atomic apply (whole batch rejected on any op failure, generation must advance by 1, root validated for exactly one child post-apply)
• LuiNodeView / LuiRender / LuiKindRules — per-kind Compose renderers + property validation matrix
• LuiTheme — semantic token mapping (glass, surface-container-high, muted/secondary/accent, spacing/radii/typography) onto a Material3 colorScheme, tuned for both light and dark
• LuiExtension — extension registry with composable builders + event emit; LuiSplit — split-view/branch/pane/tab port (draggable ratio divider emitting ratio-changed, tab bar emitting tab-selected/tab-closed/pane-focused)
• LuiBridge + lui_jni_bridge.c — JNI bridge under the lui_kotlin_* named-value prefix; same lock discipline as the C bridge (patch callback runs under the OCaml domain lock: copies the JSON out and dispatches UI-side)

Codegen: renderKotlin emitter in tooling/generate_component_schema.mjs → LuiWireSchema.kt (kind/property enums + support matrices). Reuses the swift name field; the one collision (name → propName, Enum.name) is handled in the generator.

Host wiring: KotlinHost in host_kind (protocol + host_code 4), kotlin host name, {android,kotlin} in the all/splits extension profiles, native-card moved to a new web-and-kotlin profile, fingerprint literals recomputed across all split host sources + tests, lui_element_combine mobile branches restored keyed on KotlinHost. components_bridge.ml registers lui_kotlin and gains the missing extension_event entry point (shared gap — the split/markdown/navigation bridges already had it).

Gallery app (examples/components/android, appId dev.lui.components, matching the Maestro flow): loads liblui_components.so, registers split + gallery extensions, renders the tree. CMake falls back to a stub when the OCaml .so is absent.

Screenshots (Paparazzi goldens, phone size)

Light	Dark

Kind coverage

All 88 wire kinds accepted; rendered: 86. No-op (documented, mirrors other backends):

• filePreview — platform-native file preview has no generic Compose equivalent
• br — semantic line break, layout is handled by text kinds

Modal surfaces (dialog/sheet/popover) render via LuiModalSurface; remaining kinds render through dedicated per-kind composables or the chrome-surface + children path.

Verification

• dune runtest -j 4: 66/66 green (incl. fingerprint drift check now covering LuiSplit.kt)
• node --test tooling/test/*.mjs: 6/6
• gradle :lui:testDebugUnitTest: 18 JVM wire/store tests green
• gradle :lui:verifyPaparazziDebug: 4 goldens green (light + dark)
• gradle -p examples/components/android assembleDebug: gallery APK builds

Stubbed / gaps

• liblui_components.so can't be built on this VM (lg Android OCaml toolchain absent); CMake compiles lui_jni_bridge_stub.c so the app still builds — run tooling/mobile/build_components_android.sh on a machine with the toolchain for the real runtime
• Split pane mounts only the selected tab (matches web); drag-and-drop tab re-order events are declared but drop-target UI is minimal
• compileSdk pinned to 35 — Paparazzi 1.3.5 breaks on 36 (android.os.Build reflection); bump when Paparazzi supports it

For the chat-Android session

The dev.lui public surface is aligned with the module vendored in logseq/chat#37 — the includeBuild "../../lui/platform/android" swap is a pure delete:

• Gradle module: project(":lui") at platform/android/lui (composite include via includeBuild)
• LuiBackend(onEvent: (LuiEvent) -> Unit, extensions: LuiExtensionRegistry, icons: LuiIconResolver); applyJson(raw: String?): Boolean, Content(rootId: Long = -1L) (all roots when negative), node(id: Long)
• LuiEvent sealed class, node: Long ids everywhere; LuiEvent.Extension(node, identifier, name, values: Map<String, Any?>)
• LuiIconResolver fun interface { icon(name): ImageVector? } + or() + DEFAULT — app:-prefixed names fall through to the app-level resolver
• LocalLuiThemeDark (Boolean? — null follows the system), LuiTheme(dark, semanticColors, ...) { ... }
• Extensions: registry.register(id, fingerprint) { context -> ... }, context.string/int/double/flag/property<T>, context.emit(name, Map<String, Any?>), context.Children()
• LuiBridge.start(libraryName) { patchJson -> backend.applyJson(patchJson) } — optional; calling NativeCore.lui* directly works identically

Link to Devin session: https://app.devin.ai/sessions/78ea579791324d83bc9dc95abc89fdfe
Open in Devin Desktop: https://app.devin.ai/desktop/session/78ea579791324d83bc9dc95abc89fdfe?variant=devin
Requested by: @tiensonqin

[devin-ai-integration]

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