feat: move session history to a dedicated history screen (#175)

* feat: move session history to a dedicated history screen

Closes #159.

* fix(ci): fix ktlint style issues and unresolved NavigationController reference

app/src/main/java/com/m57/hermescontrol/ui/sessions/SessionsScreen.kt

@@ -0,0 +1,130 @@
+package com.m57.hermescontrol.ui.sessions
+
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.width
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.History
+import androidx.compose.material3.Card
+import androidx.compose.material3.CardDefaults
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.font.FontWeight
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.m57.hermescontrol.ChatScreen
+import com.m57.hermescontrol.NavigationController
+import com.m57.hermescontrol.theme.LocalSpacing
+import com.m57.hermescontrol.ui.common.EmptyState
+import com.m57.hermescontrol.ui.common.ErrorState
+import com.m57.hermescontrol.ui.common.HermesScaffold
+import com.m57.hermescontrol.ui.common.LoadingState
+import com.m57.hermescontrol.ui.common.listContentPadding
+import com.m57.hermescontrol.ui.common.listItemSpacing
+
+@Composable
+fun SessionsScreen(
+    modifier: Modifier = Modifier,
+    onOpenDrawer: (() -> Unit)? = null,
+    viewModel: SessionsViewModel = viewModel { SessionsViewModel() },
+) {
+    val state by viewModel.uiState.collectAsStateWithLifecycle()
+    val spacing = LocalSpacing.current
+
+    LaunchedEffect(Unit) {
+        viewModel.loadSessions()
+    }
+
+    HermesScaffold(
+        title = { Text("History") },
+        onOpenDrawer = onOpenDrawer,
+        isRefreshing = state.isLoading,
+        onRefresh = { viewModel.loadSessions() },
+        modifier = modifier,
+    ) {
+        when {
+            state.isLoading && state.sessions.isEmpty() -> {
+                LoadingState()
+            }
+
+            state.errorMessage != null -> {
+                ErrorState(
+                    message = state.errorMessage ?: "Unknown error",
+                    onRetry = { viewModel.loadSessions() },
+                )
+            }
+
+            state.sessions.isEmpty() -> {
+                EmptyState(
+                    title = "No history",
+                    subtitle = "Previous chat sessions from Hermes will appear here.",
+                    icon = Icons.Filled.History,
+                )
+            }
+
+            else -> {
+                LazyColumn(
+                    modifier = Modifier.fillMaxWidth(),
+                    contentPadding = listContentPadding,
+                    verticalArrangement = listItemSpacing,
+                ) {
+                    items(state.sessions) { session ->
+                        Card(
+                            modifier =
+                                Modifier
+                                    .fillMaxWidth()
+                                    .clickable {
+                                        NavigationController.pendingSessionId = session.id
+                                        NavigationController.navigateTo(ChatScreen)
+                                    },
+                            colors =
+                                CardDefaults.cardColors(
+                                    containerColor = MaterialTheme.colorScheme.surfaceContainer,
+                                ),
+                        ) {
+                            Column(
+                                modifier = Modifier.padding(spacing.md),
+                            ) {
+                                Text(
+                                    text = session.title ?: "Untitled",
+                                    style = MaterialTheme.typography.titleMedium,
+                                    fontWeight = FontWeight.Bold,
+                                )
+                                Spacer(modifier = Modifier.height(spacing.xs))
+                                Row(
+                                    verticalAlignment = Alignment.CenterVertically,
+                                ) {
+                                    Text(
+                                        text = "${session.message_count ?: 0} messages",
+                                        style = MaterialTheme.typography.bodyMedium,
+                                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                                    )
+                                    if (!session.status.isNullOrBlank()) {
+                                        Spacer(modifier = Modifier.width(spacing.sm))
+                                        Text(
+                                            text = "•  ${session.status}",
+                                            style = MaterialTheme.typography.bodyMedium,
+                                            color = MaterialTheme.colorScheme.primary,
+                                        )
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+}

app/src/main/java/com/m57/hermescontrol/ui/sessions/SessionsViewModel.kt

@@ -0,0 +1,55 @@
+package com.m57.hermescontrol.ui.sessions
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.m57.hermescontrol.data.model.SessionInfo
+import com.m57.hermescontrol.data.remote.ApiClient
+import com.m57.hermescontrol.data.remote.NetworkResult
+import com.m57.hermescontrol.data.remote.safeApiCall
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+
+data class SessionsUiState(
+    val isLoading: Boolean = false,
+    val sessions: List<SessionInfo> = emptyList(),
+    val errorMessage: String? = null,
+)
+
+class SessionsViewModel : ViewModel() {
+    private val _uiState = MutableStateFlow(SessionsUiState())
+    val uiState: StateFlow<SessionsUiState> = _uiState.asStateFlow()
+
+    fun loadSessions() {
+        _uiState.update { it.copy(isLoading = true, errorMessage = null) }
+        viewModelScope.launch {
+            val result =
+                withContext(Dispatchers.IO) {
+                    safeApiCall { ApiClient.hermesApi.getSessions() }
+                }
+            when (result) {
+                is NetworkResult.Success -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            sessions = result.data?.sessions.orEmpty(),
+                        )
+                    }
+                }
+
+                is NetworkResult.Failure -> {
+                    _uiState.update {
+                        it.copy(
+                            isLoading = false,
+                            errorMessage = "Failed to load sessions: ${result.error.message}",
+                        )
+                    }
+                }
+            }
+        }
+    }
+}