refactor: improve architecture consistency and robustness

- Add ConnectChatUseCase/DisconnectChatUseCase to eliminate direct Repository dependency from ViewModel
- Make ImageFileStorage.saveFromUri suspend with withContext(Dispatchers.IO) to avoid blocking
- Inject CoroutineScope into WebSocketClient instead of internal creation for testability
- Add Log.w to all silently swallowed exceptions in WebSocketClient and MessageMapper
- Add fallbackToDestructiveMigration to Room database builder

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

android/app/src/main/java/io/picoclaw/android/di/AppModule.kt

@@ -9,6 +9,8 @@ import io.picoclaw.android.core.data.local.ImageFileStorage
 import io.picoclaw.android.core.data.remote.WebSocketClient
 import io.picoclaw.android.core.data.repository.ChatRepositoryImpl
 import io.picoclaw.android.core.domain.repository.ChatRepository
+import io.picoclaw.android.core.domain.usecase.ConnectChatUseCase
+import io.picoclaw.android.core.domain.usecase.DisconnectChatUseCase
 import io.picoclaw.android.core.domain.usecase.LoadMoreMessagesUseCase
 import io.picoclaw.android.core.domain.usecase.ObserveConnectionUseCase
 import io.picoclaw.android.core.domain.usecase.ObserveMessagesUseCase
@@ -33,7 +35,7 @@ val appModule = module {
             androidContext(),
             AppDatabase::class.java,
             "picoclaw.db"
-        ).build()
+        ).fallbackToDestructiveMigration(dropAllTables = true).build()
     }
     single { get<AppDatabase>().messageDao() }
 
@@ -50,7 +52,7 @@ val appModule = module {
     }
 
     // WebSocketClient
-    single { WebSocketClient(get()) }
+    single { WebSocketClient(get(), get()) }
 
     // ImageFileStorage
     single { ImageFileStorage(androidContext()) }
@@ -63,7 +65,9 @@ val appModule = module {
     factory { ObserveMessagesUseCase(get()) }
     factory { ObserveConnectionUseCase(get()) }
     factory { LoadMoreMessagesUseCase(get()) }
+    factory { ConnectChatUseCase(get()) }
+    factory { DisconnectChatUseCase(get()) }
 
     // ViewModel
-    viewModel { ChatViewModel(get(), get(), get(), get(), get()) }
+    viewModel { ChatViewModel(get(), get(), get(), get(), get(), get()) }
 }

android/core/data/src/main/java/io/picoclaw/android/core/data/local/ImageFileStorage.kt

@@ -5,6 +5,8 @@ import android.graphics.BitmapFactory
 import android.net.Uri
 import android.util.Base64
 import io.picoclaw.android.core.domain.model.ImageData
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
 import java.io.File
 import java.util.UUID
 
@@ -17,7 +19,7 @@ class ImageFileStorage(private val context: Context) {
         val base64: String
     )
 
-    fun saveFromUri(uriString: String): SaveResult {
+    suspend fun saveFromUri(uriString: String): SaveResult = withContext(Dispatchers.IO) {
         val bytes = context.contentResolver.openInputStream(Uri.parse(uriString))?.use {
             it.readBytes()
         } ?: error("Cannot read URI: $uriString")
@@ -28,7 +30,7 @@ class ImageFileStorage(private val context: Context) {
         val opts = BitmapFactory.Options().apply { inJustDecodeBounds = true }
         BitmapFactory.decodeFile(file.absolutePath, opts)
 
-        return SaveResult(
+        SaveResult(
             imageData = ImageData(file.absolutePath, opts.outWidth, opts.outHeight),
             base64 = Base64.encodeToString(bytes, Base64.NO_WRAP)
         )

android/core/data/src/main/java/io/picoclaw/android/core/data/mapper/MessageMapper.kt

@@ -1,5 +1,6 @@
 package io.picoclaw.android.core.data.mapper
 
+import android.util.Log
 import io.picoclaw.android.core.data.local.entity.MessageEntity
 import io.picoclaw.android.core.data.remote.dto.WsIncoming
 import io.picoclaw.android.core.data.remote.dto.WsOutgoing
@@ -23,7 +24,8 @@ object MessageMapper {
                 Json.decodeFromString<List<ImageEntry>>(it).map { e ->
                     ImageData(e.path, e.width, e.height)
                 }
-            } catch (_: Exception) {
+            } catch (e: Exception) {
+                Log.w("MessageMapper", "Failed to parse image path list", e)
                 emptyList()
             }
         } ?: emptyList()

android/core/data/src/main/java/io/picoclaw/android/core/data/remote/WebSocketClient.kt

@@ -1,5 +1,6 @@
 package io.picoclaw.android.core.data.remote
 
+import android.util.Log
 import io.ktor.client.HttpClient
 import io.ktor.client.plugins.websocket.webSocket
 import io.ktor.websocket.Frame
@@ -9,9 +10,7 @@ import io.picoclaw.android.core.data.remote.dto.WsIncoming
 import io.picoclaw.android.core.data.remote.dto.WsOutgoing
 import io.picoclaw.android.core.domain.model.ConnectionState
 import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -24,7 +23,10 @@ import kotlinx.coroutines.launch
 import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.Json
 
-class WebSocketClient(private val client: HttpClient) {
+class WebSocketClient(
+    private val client: HttpClient,
+    private val scope: CoroutineScope
+) {
 
     private val _connectionState = MutableStateFlow(ConnectionState.DISCONNECTED)
     val connectionState: StateFlow<ConnectionState> = _connectionState.asStateFlow()
@@ -35,7 +37,6 @@ class WebSocketClient(private val client: HttpClient) {
     private var session: WebSocketSession? = null
     private var connectJob: Job? = null
     private val json = Json { ignoreUnknownKeys = true }
-    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.IO)
 
     var wsUrl: String = "ws://127.0.0.1:18793/ws"
 
@@ -56,12 +57,14 @@ class WebSocketClient(private val client: HttpClient) {
                                 try {
                                     val msg = json.decodeFromString<WsOutgoing>(text)
                                     _incomingMessages.emit(msg)
-                                } catch (_: Exception) {
+                                } catch (e: Exception) {
+                                    Log.w(TAG, "Failed to parse WebSocket message", e)
                                 }
                             }
                         }
                     }
-                } catch (_: Exception) {
+                } catch (e: Exception) {
+                    Log.w(TAG, "WebSocket connection error", e)
                 }
                 session = null
                 _connectionState.value = ConnectionState.RECONNECTING
@@ -82,12 +85,14 @@ class WebSocketClient(private val client: HttpClient) {
         return try {
             session?.send(Frame.Text(json.encodeToString(dto)))
             true
-        } catch (_: Exception) {
+        } catch (e: Exception) {
+            Log.w(TAG, "Failed to send WebSocket message", e)
             false
         }
     }
 
     companion object {
+        private const val TAG = "WebSocketClient"
         private const val INITIAL_DELAY = 1000L
         private const val MAX_DELAY = 30000L
     }

android/core/domain/src/main/java/io/picoclaw/android/core/domain/usecase/ConnectChatUseCase.kt

@@ -0,0 +1,9 @@
+package io.picoclaw.android.core.domain.usecase
+
+import io.picoclaw.android.core.domain.repository.ChatRepository
+
+class ConnectChatUseCase(private val repository: ChatRepository) {
+    operator fun invoke() {
+        repository.connect()
+    }
+}

android/core/domain/src/main/java/io/picoclaw/android/core/domain/usecase/DisconnectChatUseCase.kt

@@ -0,0 +1,9 @@
+package io.picoclaw.android.core.domain.usecase
+
+import io.picoclaw.android.core.domain.repository.ChatRepository
+
+class DisconnectChatUseCase(private val repository: ChatRepository) {
+    operator fun invoke() {
+        repository.disconnect()
+    }
+}

android/feature/chat/src/main/java/io/picoclaw/android/feature/chat/ChatViewModel.kt

@@ -2,7 +2,8 @@ package io.picoclaw.android.feature.chat
 
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
-import io.picoclaw.android.core.domain.repository.ChatRepository
+import io.picoclaw.android.core.domain.usecase.ConnectChatUseCase
+import io.picoclaw.android.core.domain.usecase.DisconnectChatUseCase
 import io.picoclaw.android.core.domain.usecase.LoadMoreMessagesUseCase
 import io.picoclaw.android.core.domain.usecase.ObserveConnectionUseCase
 import io.picoclaw.android.core.domain.usecase.ObserveMessagesUseCase
@@ -18,14 +19,15 @@ class ChatViewModel(
     private val observeMessages: ObserveMessagesUseCase,
     private val observeConnection: ObserveConnectionUseCase,
     private val loadMoreMessages: LoadMoreMessagesUseCase,
-    private val repository: ChatRepository
+    private val connectChat: ConnectChatUseCase,
+    private val disconnectChat: DisconnectChatUseCase
 ) : ViewModel() {
 
     private val _uiState = MutableStateFlow(ChatUiState())
     val uiState: StateFlow<ChatUiState> = _uiState.asStateFlow()
 
     init {
-        repository.connect()
+        connectChat()
 
         viewModelScope.launch {
             observeMessages().collect { messages ->
@@ -80,6 +82,6 @@ class ChatViewModel(
 
     override fun onCleared() {
         super.onCleared()
-        repository.disconnect()
+        disconnectChat()
     }
 }