v0.2.0: Dirty tracking — dirty-mixin, mark-clean, mark-dirty

- dirty-mixin class with dirty slot (initform t)
- mark-clean clears dirty flag
- mark-dirty sets dirty flag
- 3 tests: default-dirty, clean, dirty-cycle
- ROADMAP.org: v0.2.0 all tasks DONE
- 31 component tests, 100% GREEN

src/components/package.lisp

@@ -17,5 +17,7 @@
    #:text-fg #:text-bg #:text-wrap-mode
    #:render-text
    ;; Utilities (for tests)
-   #:word-wrap #:split-string))
+   #:word-wrap #:split-string
+   ;; Dirty tracking
+   #:dirty-mixin #:dirty-p #:mark-clean #:mark-dirty))
 (in-package :cl-tui.box)