Stop composer layout recursion on spaces

app-rust/src/ui/composer.rs

@@ -112,6 +112,13 @@ where
     // the transcript: measured at 58px of stray text for a 475px message
     // in a 417px box.
     let content = field
+        // A wrapping editor occupies the composer's width even when its
+        // current text is short. Without this inner constraint the vertical
+        // ScrollArea reports the text's narrow natural width to Pad; settling
+        // then offers that width back to the editor, where a trailing space
+        // wraps and doubles its height. The next parent pass restores the
+        // wide one-line answer, so the two layouts have no fixed point.
+        .width(rest(1))
         // `scrollable_to_end`: what is being typed is at the end, so a
         // message longer than the six lines shown holds that end.
         .scrollable(Axis::Y, Pin::End)