fix(mobile): gate the tool detail panel on having detail (STA-3333)

The Tools toggle opens every row at once, bypassing the row's tap guard,
so a row with nothing to expand rendered its own label again underneath
itself — and the tap that would dismiss it is a no-op. Matches desktop.

mobile/src/session/MobileNativeChatMessage.test.ts

@@ -141,4 +141,14 @@ describe('MobileNativeChatMessage', () => {
       '{\n  "cmd": "git status",\n  "description": "Inspect changes"\n}'
     )
   })
+
+  it('does not echo the row label as detail when a row has nothing to expand', () => {
+    // The Tools toggle opens every row at once, bypassing the tap guard — a row
+    // whose formatted input is its own label would echo itself in a panel that
+    // no tap can dismiss.
+    const tree = render(toolMessage([{ type: 'tool-call', name: 'ListTodos', input: '{}' }]), {
+      toolsExpanded: true
+    })
+    expect(textIn(tree.root).filter((text) => text === '{}')).toHaveLength(1)
+  })
 })

mobile/src/session/MobileNativeChatMessage.tsx

@@ -109,6 +109,10 @@ function ToolLine({
     result !== undefined ||
     preview.length > 40 ||
     (call !== undefined && isStructuredToolInput(call.input))
+  // The group toggle opens every line at once, bypassing the tap guard, so the
+  // panel has to consult it too — else a detail-less row echoes its own label
+  // under itself and no tap can dismiss it.
+  const showDetail = hasDetail && expanded
   // A tool that targets a file (Read/Edit/Write…) renders its preview as a
   // tappable link that opens the file, independent of the line's expand tap.
   const filePath = call ? toolFilePath(call.input) : null
@@ -120,7 +124,7 @@ function ToolLine({
         onPress={() => hasDetail && setExpanded((v) => !v)}
         hitSlop={6}
       >
-        {expanded ? (
+        {showDetail ? (
           <ChevronDown size={15} color={colors.textMuted} strokeWidth={2} />
         ) : (
           <SquareChevronRight size={15} color={colors.textMuted} strokeWidth={2} />
@@ -137,7 +141,7 @@ function ToolLine({
           </Text>
         ) : null}
       </Pressable>
-      {expanded ? (
+      {showDetail ? (
         <View style={styles.toolDetail}>
           {callDiff ? <DiffView lines={callDiff} /> : null}
           {callDetail ? <Text style={styles.mono}>{callDetail}</Text> : null}