End a subagent on its own end_turn, not the parent's tool_result, and give the expander a touch-sized row

The Agent tool runs subagents in the background, so the parent's result
arrives at launch while the subagent works on for minutes; finishing on it
read a running agent as finished with a transcript cut off at launch. A
subagent now ends on its own message_delta end_turn, and a later line for a
finished one reopens it, since a background agent can be messaged again.

The card's expander row was only the chevron's height, so a tap for it
landed on the first subcard; it is the platform's 48dp minimum now.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

app/androidApp/src/main/kotlin/com/example/aiapp/SessionListScreen.kt

@@ -11,6 +11,7 @@ import androidx.compose.foundation.layout.Spacer
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
@@ -396,10 +397,15 @@ private fun SessionCard(
                 // already on screen -- see UI_RULES on a control not displacing the text beside it.
                 if (session.subagents > 0) {
                     Spacer(Modifier.height(8.dp))
+                    // The platform's minimum touch height, not the chevron's own ten or so dp:
+                    // at the chevron's height a tap meant for it landed on the first subcard
+                    // beneath and opened a subagent instead.
                     Row(
                         horizontalArrangement = Arrangement.Center,
+                        verticalAlignment = Alignment.CenterVertically,
                         modifier =
                             Modifier.fillMaxWidth()
+                                .heightIn(min = 48.dp)
                                 .clickable(enabled = !deleting, onClick = onToggleSubagents)
                                 .semantics {
                                     contentDescription =