fix(mobile): keep the live text's actions sheet on the block it was opened for

On Android the sheet opened by a long press on the live reasoning was a flag gated on a live
block: it vanished when the block ended, mid Select text, and the stale flag reopened it
unprompted on the next block. The sheet now holds the message it was opened for.

mobile/src/session/MobileNativeChatLiveLine.android.test.ts

@@ -74,4 +74,50 @@ describe('MobileNativeChatLiveLine on Android', () => {
     act(() => sheet!.props.onClose())
     expect(byType('MessageActionsSheet')).toHaveLength(0)
   })
+
+  it('keeps the sheet through the block ending, and never opens one for the next by itself', () => {
+    const line = (reasoning: NativeChatLiveReasoning | null) =>
+      createElement(MobileNativeChatLiveLine, {
+        line: { thinking: true, activityText: null, reasoning, reasoningExpanded: true },
+        onToggleReasoning: vi.fn(),
+        fontScale: 1
+      })
+    act(() => {
+      renderer = create(line(block))
+    })
+    act(() => byType('ReasoningBody')[0]!.props.onLongPress())
+    // The block ends while the reader copies or selects it.
+    act(() => renderer!.update(line(null)))
+    expect(byType('MessageActionsSheet').map((sheet) => sheet.props.message)).toEqual([
+      block.message
+    ])
+    act(() => byType('MessageActionsSheet')[0]!.props.onClose())
+    const next: NativeChatLiveReasoning = {
+      message: { ...block.message, id: 'r-2' },
+      markdown: 'Next thought'
+    }
+    act(() => renderer!.update(line(next)))
+    expect(byType('MessageActionsSheet')).toHaveLength(0)
+  })
+
+  it('opens no sheet for the next block when the first ends with the sheet open', () => {
+    const line = (reasoning: NativeChatLiveReasoning | null) =>
+      createElement(MobileNativeChatLiveLine, {
+        line: { thinking: true, activityText: null, reasoning, reasoningExpanded: true },
+        onToggleReasoning: vi.fn(),
+        fontScale: 1
+      })
+    act(() => {
+      renderer = create(line(block))
+    })
+    act(() => byType('ReasoningBody')[0]!.props.onLongPress())
+    act(() => renderer!.update(line(null)))
+    const next: NativeChatLiveReasoning = {
+      message: { ...block.message, id: 'r-2' },
+      markdown: 'Next thought'
+    }
+    act(() => renderer!.update(line(next)))
+    // Still the first block's sheet, the one the reader opened; none for r-2.
+    expect(byType('MessageActionsSheet').map((sheet) => sheet.props.message.id)).toEqual(['r-1'])
+  })
 })

mobile/src/session/MobileNativeChatLiveLine.tsx

@@ -3,6 +3,7 @@ import { ActivityIndicator, Pressable, StyleSheet, Text, View } from 'react-nati
 import { ChevronRight } from 'lucide-react-native'
 import { nativeChatReasoningDisclosureKey } from '../../../src/shared/native-chat-reasoning-row'
 import { formatNativeChatActiveTurnLabel } from '../../../src/shared/native-chat-turn-status'
+import type { NativeChatMessage } from '../../../src/shared/native-chat-types'
 import { INLINE_TEXT_SELECTION } from '../components/inline-text-selection'
 import { colors, spacing, typography } from '../theme/mobile-theme'
 import { MobileNativeChatMessageActionsSheet } from './MobileNativeChatMessageActionsSheet'
@@ -28,8 +29,10 @@ export function MobileNativeChatLiveLine({
   const open = reasoning !== null && reasoningExpanded
   const label = formatNativeChatActiveTurnLabel(line)
   // Android has no inline selection; the finished row's long-press sheet copies the live text too.
-  const [actionsOpen, setActionsOpen] = useState(false)
-  const openActions = useCallback(() => setActionsOpen(true), [])
+  // It holds the block it opened for, so it outlives that block ending and never reopens by itself.
+  const [actionsFor, setActionsFor] = useState<NativeChatMessage | null>(null)
+  const liveMessage = reasoning?.message ?? null
+  const openActions = useCallback(() => setActionsFor(liveMessage), [liveMessage])
   return (
     <View>
       {/* One element for every state of the line, so TalkBack hears each new label; the body
@@ -70,10 +73,10 @@ export function MobileNativeChatLiveLine({
           />
         </View>
       ) : null}
-      {reasoning && actionsOpen ? (
+      {actionsFor ? (
         <MobileNativeChatMessageActionsSheet
-          message={reasoning.message}
-          onClose={() => setActionsOpen(false)}
+          message={actionsFor}
+          onClose={() => setActionsFor(null)}
         />
       ) : null}
     </View>