Attach the restore hook only while there is a restore

`onPlaced` on the transcript content is the one callback left that would
run every frame, and on all but the two frames of a restore it looks at
a null and returns. Attaching it only while a position is waiting says
that in the modifier chain rather than in a branch inside it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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

@@ -262,7 +262,10 @@ fun TranscriptColumn(
             .fillMaxWidth()
             // Once for the whole list, not once per row: this is where a saved position is put
             // back, and by placement the scroll container's own measurements describe this layout.
-            .onPlaced { state.placed() }
+            // Only while there is a position waiting to be put back. `onPlaced` is the one hook
+            // here that would otherwise run on every frame, and it has nothing to do on all but
+            // the two frames of a restore.
+            .then(if (state.settling) Modifier.onPlaced { state.placed() } else Modifier)
             // One gesture detector for the whole list; see [TranscriptScroll.tappedHigh]. On the
             // initial pass and consuming nothing, so every control inside still gets the gesture
             // exactly as it would have.