Integrate the real LUI Kotlin backend (KotlinHost)

[tiensonqin]

Summary

Integrates the real LUI Kotlin backend (logseq/lui#135, merged as lui@afeb4cc) and renames the Android host profile FlutterHost → KotlinHost end to end. The vendored android/lui shim is gone; :lui now resolves to ../lui/platform/android/lui as a module include — the same consumption model as lui's examples/components/android and apple/'s path-dep on ../lui/platform/apple.

• logseq_chat.opam: lui pin bumped a2d1cfa → afeb4cc82c346deddb304248fd74d102b5907863 (feat(android): Kotlin/Jetpack Compose backend lui#135, merged).
• Host codes (matching components_bridge.ml in lui: 1 Web, 2 SwiftUI, 4 Kotlin, 6 GPUI): Native_bridge.host_kind is now the full table; logseq_chat_lui_initialize call sites use hostCode = 4 on Android (LogseqChatNativeBridge.initialize) and 2 on iOS (LGChatRuntime.start — previously defaulted to 1, which now resolves to WebHost).
• shared/: every FlutterHost → KotlinHost, android/flutter → android/kotlin in extension profile strings and the fingerprint literals in app_test.ml, apple/ extension fingerprints, and ChatExtensions.kt; all flutter_* identifiers renamed to kotlin_*. rg -il flutter is now zero outside .git/_build/duniverse.
• shared/ reactive migration: the new lui.ppx expands a bare reactive f s to dyn f s (element position, f : 'a -> t). All bare reactive calls feeding *_signal setters and let bindings are now explicit Signal.map; ~p:(reactive ..) labeled forms are unchanged so the ppx still produces prop signals.
• LuiDispatch: handles the widened upstream LuiEvent sealed class — PressDetail, Pointer{Down,Up,Enter,Leave}, ContextMenuPress, PressModifiers, Load are dropped because the chat FFI (logseq_chat_core_ffi.h) exports no entries for them, matching upstream dispatchToBridge's treatment of unmapped events.
• android/settings.gradle.kts: include(":lui") with projectDir = ../../lui/platform/android/lui. :lui test tasks are disabled in this build — its paparazzi suite needs the standalone AGP 8.6.1 platform/android build.

Drift between my vendored dev.lui surface and the real backend

Minimal — every symbol the app imports (LuiBackend, LuiEvent, LuiExtensionContext, LuiExtensionRegistry, LuiIconResolver, LocalLuiThemeDark) exists upstream with the same shape. The only deltas handled:

1. LuiEvent grew the pointer/context-menu/load variants listed above.
2. AGP version mismatch (needs upstream attention): platform/android/lui/build.gradle.kts applies org.jetbrains.kotlin.android + plugin.serialization + app.cash.paparazzi under AGP 8.6.1, while this app uses AGP 9.1 (android.builtInKotlin) — Gradle forbids mixed AGP versions in one build, and AGP 9 dropped the kotlin-android plugin. To verify locally I edited the ../lui checkout to drop those three plugin ids (no @Serializable types exist, and paparazzi is only needed by the backend's own tests). That edit is local-only — the lui repo should ship an AGP-9-compatible module build (or the host must stay on AGP 8).

Verification

• dune build @shared/native/runtest — 719 tests green.
• cd android && ./gradlew assembleDebug assembleProfile test — green against the real backend (:app unit tests pass; :lui tests disabled as noted).
• test-android-native-script.sh, test-no-skip-support.sh, test-android-e2e-runner.sh pass.
• Fresh liblogseq_chat_core.so (x86_64) + profile APK on the chat_test emulator: app launches, take_effect/apply_snapshot/apply_host_update cycle confirmed in logcat, auth screen renders via the real backend:

Link to Devin session: https://app.devin.ai/sessions/c2d54f90729342239d4afea72f403e41
Open in Devin Desktop: https://app.devin.ai/desktop/session/c2d54f90729342239d4afea72f403e41?variant=devin
Requested by: @tiensonqin

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring