v0.6.0: ScrollBox + TabBar — container components

ScrollBox:
- Container with vertical/horizontal scroll, viewport culling
- Scroll offset (:scroll-y, :scroll-x) with clamp to valid bounds
- Scrollbars rendered when content exceeds viewport
- Sticky scroll (auto-scroll to bottom on content change)
- Component protocol: component-children, component-layout-node

TabBar:
- Horizontal tab row with active/inactive styling
- tab-bar-next/prev (wraps around), tab-bar-select, tab-bar-handle-key
- Tab title rendering with overflow truncation (ellipsis)
- Component protocol: component-layout-node

26 scrollbox+tabbar tests, 100% GREEN:
171 total (27 backend + 58 box + 60 input + 26 scrollbox)

Review fixes applied:
- Removed duplicate definitions (org per-function blocks are prose-only)
- Fixed ASDF test path (../../tests/...)
- Version bumped to 0.6.0
- Added clamp-scroll export
- Added tab-bar-next/prev/select/handle-key tests
- Added scroll clamp boundary tests

cl-tui.asd

@@ -2,7 +2,7 @@
 (asdf:defsystem :cl-tui
   :description "Reusable Common Lisp Terminal UI Framework"
   :author "Amr Gharbeia"
-  :version "0.5.0"
+  :version "0.6.0"
   :license "TBD"
   :depends-on (:fiveam :sb-posix)
   :components
@@ -28,7 +28,11 @@
      (:file "input" :depends-on ("input-package" "dirty" "box"))
      (:file "text-input" :depends-on ("input-package" "input" "box"))
      (:file "textarea" :depends-on ("input-package" "input" "box"))
-     (:file "keybindings" :depends-on ("input-package" "input")))))
+     (:file "keybindings" :depends-on ("input-package" "input"))
+     ;; Container components (v0.6.0)
+     (:file "container-package" :depends-on ("package" "input-package"))
+     (:file "scrollbox" :depends-on ("container-package" "dirty" "box"))
+     (:file "tabbar" :depends-on ("container-package" "dirty" "box"))))
   :in-order-to ((test-op (test-op :cl-tui-tests))))
 
 (asdf:defsystem :cl-tui-tests
@@ -47,11 +51,13 @@
      (:file "dirty-tests")
      (:file "render-tests")
      (:file "theme-tests")
-     (:file "input-tests"))))
+     (:file "input-tests")
+     (:file "scrollbox-tabbar-tests" :pathname "../../tests/scrollbox-tabbar-tests.lisp"))))
   :perform (test-op (o c)
-             (dolist (suite '((:cl-tui-backend-test "BACKEND-SUITE")
+              (dolist (suite '((:cl-tui-backend-test "BACKEND-SUITE")
                               (:cl-tui-box-test "BOX-SUITE")
-                              (:cl-tui-input-test "INPUT-SUITE")))
+                              (:cl-tui-input-test "INPUT-SUITE")
+                              (:cl-tui-scrollbox-test "SCROLLBOX-SUITE")))
                (let* ((pkg (find-package (first suite)))
                       (s (and pkg (find-symbol (second suite) pkg))))
                  (when s