Restore reading backspace if typing with autoread disabled.

internal/reader/echo.go

@@ -138,3 +138,22 @@ func all_spaces(cells []rune) bool {
 	}
 	return true
 }
+
+// Deletion echo uses only text verified against the previous screen. Like
+// typing echo, it remains available with autoread/cursor/character echo off,
+// but never exposes text excluded by a live region.
+func (r *Reader) deletion_echo(deleted []rune, next screen.Snapshot) []presentation.Message {
+	var allowed []rune
+	for index, char := range deleted {
+		if r.region_state().allows(next.X+index, next.Y, next.Cols, false, true) {
+			allowed = append(allowed, char)
+		}
+	}
+	if len(allowed) == 1 {
+		return []presentation.Message{presentation.Character_message(allowed[0])}
+	}
+	if len(allowed) > 1 {
+		return []presentation.Message{{Text: string(allowed)}}
+	}
+	return nil
+}