fix(#283): apply minor performance optimizations for Chat (#315)

* fix(#283): apply minor performance optimizations for Chat

- Optimized `ChatScreen.kt` background gradient to use `remember` block correctly keyed by individual colors to avoid reallocation on recomposition.
- Removed redundant `luminance()` calculation caching inside `ChatBubble.kt` to preserve dynamic theme changes correctly while keeping code concise.
- Refactored `pendingRequests` timeout loop in `ChatViewModel.kt` to use `iterator.remove()` instead of generating a new filtered list.
- Converted `SideEffect` for `initialSessionId` assignment in `ChatScreen` to `remember` block to guarantee synchronous setup before WebSocket processes it.
- Initialized an explicit OkHttp `ConnectionPool` in `ApiClient` to survive client rebuilds.

These changes resolve Low-severity performance findings (PERF-22 to PERF-26) mentioned in issue #283 while ensuring maintainability and preserving dynamic theming.

* fix(#283): apply minor performance optimizations for Chat

- Optimized `ChatScreen.kt` background gradient to use `remember` block correctly keyed by individual colors to avoid reallocation on recomposition.
- Removed redundant `luminance()` calculation caching inside `ChatBubble.kt` to preserve dynamic theme changes correctly while keeping code concise.
- Refactored `pendingRequests` timeout loop in `ChatViewModel.kt` to use `iterator.remove()` instead of generating a new filtered list.
- Converted `SideEffect` for `initialSessionId` assignment in `ChatScreen` to `remember` block to guarantee synchronous setup before WebSocket processes it.
- Initialized an explicit OkHttp `ConnectionPool` in `ApiClient` to survive client rebuilds.

These changes resolve Low-severity performance findings (PERF-22 to PERF-26) mentioned in issue #283 while ensuring maintainability and preserving dynamic theming.

app/src/main/java/com/m57/hermescontrol/data/remote/ApiClient.kt

@@ -24,6 +24,8 @@ object ApiClient {
     @Volatile
     private var service: HermesApiService? = null
 
+    private val connectionPool = okhttp3.ConnectionPool()
+
     /** The current [HermesApiService] instance. Lazily created on first access. */
     val hermesApi: HermesApiService
         get() {
@@ -81,6 +83,7 @@ object ApiClient {
         val okHttp =
             OkHttpClient
                 .Builder()
+                .connectionPool(connectionPool)
                 .addInterceptor(authInterceptor)
                 .addInterceptor(logging)
                 .certificatePinner(certificatePinner)

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatBubble.kt

@@ -173,17 +173,18 @@ private fun UserBubble(
             )
         val primary = MaterialTheme.colorScheme.primary
         val secondary = MaterialTheme.colorScheme.secondary
+        val onPrimary = MaterialTheme.colorScheme.onPrimary
         val avgLuminance = (primary.luminance() + secondary.luminance()) / 2f
         val userBubbleTextColor =
             if (avgLuminance > 0.5f) {
-                if (MaterialTheme.colorScheme.onPrimary.luminance() < 0.5f) {
+                if (onPrimary.luminance() < 0.5f) {
-                    MaterialTheme.colorScheme.onPrimary
+                    onPrimary
                 } else {
                     Color(0xFF1A1A24)
                 }
             } else {
-                if (MaterialTheme.colorScheme.onPrimary.luminance() > 0.5f) {
+                if (onPrimary.luminance() > 0.5f) {
-                    MaterialTheme.colorScheme.onPrimary
+                    onPrimary
                 } else {
                     Color.White
                 }
@@ -279,16 +280,17 @@ private fun AssistantBubble(
     modifier: Modifier = Modifier,
 ) {
     val bubbleColor = if (isDarkTheme) AssistantBubble else AssistantBubbleLight
+    val onSurface = MaterialTheme.colorScheme.onSurface
     val textColor =
         if (bubbleColor.luminance() > 0.5f) {
-            if (MaterialTheme.colorScheme.onSurface.luminance() < 0.5f) {
+            if (onSurface.luminance() < 0.5f) {
-                MaterialTheme.colorScheme.onSurface
+                onSurface
             } else {
                 Color(0xFF1A1A24)
             }
         } else {
-            if (MaterialTheme.colorScheme.onSurface.luminance() > 0.5f) {
+            if (onSurface.luminance() > 0.5f) {
-                MaterialTheme.colorScheme.onSurface
+                onSurface
             } else {
                 Color(0xFFE8E6EE)
             }

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatScreen.kt

@@ -75,7 +75,6 @@ import androidx.compose.material3.TextButton
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
-import androidx.compose.runtime.SideEffect
 import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
@@ -140,8 +139,9 @@ fun ChatScreen(
     // during composition — BEFORE any WebSocket event (GatewayReady) can be
     // processed. This ensures GatewayReady sees the pending session and
     // resumes it instead of creating a new empty chat (issue #240).
-    SideEffect {
+    remember(sessionId) {
         viewModel.initialSessionId = sessionId
+        true
     }
 
     // Switch to the session from a notification tap or history screen when provided.
@@ -245,15 +245,21 @@ fun ChatScreen(
         )
     }
 
+    val backgroundColor = MaterialTheme.colorScheme.background
+    val surfaceVariantColor = MaterialTheme.colorScheme.surfaceVariant
+    val primaryColor = MaterialTheme.colorScheme.primary
+
     val backgroundGradient =
+        remember(backgroundColor, surfaceVariantColor, primaryColor) {
             Brush.verticalGradient(
                 colors =
                     listOf(
-                    MaterialTheme.colorScheme.background,
+                        backgroundColor,
-                    MaterialTheme.colorScheme.surfaceVariant.copy(alpha = 0.3f),
+                        surfaceVariantColor.copy(alpha = 0.3f),
-                    MaterialTheme.colorScheme.primary.copy(alpha = 0.05f),
+                        primaryColor.copy(alpha = 0.05f),
                     ),
             )
+        }
 
     // Scroll to current search match
     LaunchedEffect(state.isSearchActive, state.currentSearchMatchIndex, state.searchMatchIndices) {

app/src/main/java/com/m57/hermescontrol/ui/chat/ChatViewModel.kt

@@ -1105,17 +1105,17 @@ class ChatViewModel(
                 while (true) {
                     delay(PENDING_REQUEST_TIMEOUT_MS)
                     val now = System.currentTimeMillis()
-                    val stale =
+                    val iterator = pendingRequests.entries.iterator()
-                        pendingRequests.entries.filter {
+                    while (iterator.hasNext()) {
-                            now - it.value.createdAt > PENDING_REQUEST_TIMEOUT_MS
+                        val entry = iterator.next()
-                        }
+                        if (now - entry.value.createdAt > PENDING_REQUEST_TIMEOUT_MS) {
-                    for (entry in stale) {
+                            iterator.remove()
-                        pendingRequests.remove(entry.key)
                             Log.w(TAG, "Request timed out: ${entry.value.method} (id=${entry.key})")
                         }
                     }
                 }
             }
+    }
 
     // ── Search ────────────────────────────────────────────────────────────