feat(#76): add testTag identifiers to composable elements for UI test targeting (#98)

Adds testTag modifiers to key interactive elements across the core
composables, enabling Espresso/Compose UI tests to locate them:

Navigation.kt  — 'nav_*' on bottom bar items, 'drawer_*' on drawer items
HermesScaffold — 'back_button', 'menu_button', 'refresh_button'
StateViews.kt  — 'loading_state', 'loading_spinner', 'error_retry_button',
                 'empty_state_action'
ChatScreen.kt  — 'chat_input', 'send_button', 'interrupt_button'

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

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

@@ -84,6 +84,7 @@ import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.platform.testTag
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.input.ImeAction
 import androidx.compose.ui.unit.dp
@@ -650,7 +651,8 @@ private fun ChatInputBar(
                         modifier =
                             Modifier
                                 .weight(1f)
-                                .heightIn(max = 140.dp),
+                                .heightIn(max = 140.dp)
+                                .testTag("chat_input"),
                         placeholder = {
                             Text(
                                 if (!isConnected) {
@@ -679,7 +681,10 @@ private fun ChatInputBar(
                         // Interrupt button
                         FilledTonalButton(
                             onClick = onInterrupt,
-                            modifier = Modifier.size(48.dp),
+                            modifier =
+                                Modifier
+                                    .size(48.dp)
+                                    .testTag("interrupt_button"),
                             shape = CircleShape,
                             contentPadding = PaddingValues(0.dp),
                         ) {
@@ -694,7 +699,10 @@ private fun ChatInputBar(
                         FilledTonalButton(
                             onClick = onSend,
                             enabled = canSend,
-                            modifier = Modifier.size(48.dp),
+                            modifier =
+                                Modifier
+                                    .size(48.dp)
+                                    .testTag("send_button"),
                             shape = CircleShape,
                             contentPadding = PaddingValues(0.dp),
                         ) {