review fixes: 3 blocking bugs + 2 improvements

B1: modern-backend now inherits from backend (was standalone class)
B2: draw-rect y-position bug — loop now tracks row offset
B3: Layout module added to ASDF system definition
I1: 6 smoke tests replaced with behavioral tests (captured output)
I3: 6 edge case tests: empty, single-child, zero-size, deep
    nesting, large padding, negative grow

Also fixed:
- Added missing make-simple-backend constructor to simple.lisp
- Added in-package to classes.lisp and simple.lisp (SBCL's load
  restores *package* after each load, breaking batch-mode loading)

cl-tui.asd

@@ -2,7 +2,7 @@
 (asdf:defsystem :cl-tui
   :description "Reusable Common Lisp Terminal UI Framework"
   :author "Amr Gharbeia"
-  :version "0.0.1"
+  :version "0.0.3"
   :license "TBD"
   :depends-on (:fiveam)
   :components
@@ -10,7 +10,11 @@
     :components
     ((:file "package")
      (:file "classes" :depends-on ("package"))
-     (:file "simple" :depends-on ("package" "classes")))))
+     (:file "simple" :depends-on ("package" "classes"))
+     (:file "modern" :depends-on ("package" "classes"))))
+   (:module "layout"
+    :components
+    ((:file "layout"))))
   :in-order-to ((test-op (test-op :cl-tui-tests))))
 
 (asdf:defsystem :cl-tui-tests
@@ -18,6 +22,9 @@
   :depends-on (:cl-tui :fiveam)
   :components
   ((:module "backend"
+    :components
+    ((:file "tests")))
+   (:module "layout"
     :components
     ((:file "tests"))))
   :perform (test-op (o c)