Function text_attach_buffer 

pub fn text_attach_buffer(
    commands: Commands<'_, '_>,
    q: Query<'_, '_, (Entity, &'_ TextContent, &'_ TextInput), (With<TextInput>, Without<TextBuffer>)>,
)

Bootstrap. For every TextInput entity without a TextBuffer, attach TextBuffer (seeded from TextContent), TextCursor (seeded from TextInput.cursor), an empty UndoStack, and the TextEditable marker. Idempotent - runs every tick at near-zero cost when nothing new is spawned.