v0.2.0: Text renderable with word-wrap and inline spans

- Text class with content, fg/bg, wrap-mode (:word or :none)
- Span class for inline styled segments (bold, italic, etc.)
- render-text dispatches through backend's draw-text
- word-wrap function splits text at word boundaries
- split-string utility for whitespace tokenization
- 9 new tests: creation, content, empty, truncation, word-wrap,
  single-word, span creation, span storage
- modern-backend now accepts :output-stream
- ASDF updated with text component
- 28 total component tests, 100% GREEN

cl-tui.asd

@@ -18,7 +18,8 @@
    (:module "src/components"
     :components
     ((:file "package")
-     (:file "box" :depends-on ("package")))))
+     (:file "box" :depends-on ("package"))
+     (:file "text" :depends-on ("package" "box")))))
   :in-order-to ((test-op (test-op :cl-tui-tests))))
 
 (asdf:defsystem :cl-tui-tests