fix: add draw-text method for raw 2D arrays

Application code (passepartout TUI) calls draw-text with a framebuffer
(2D array) as the first argument, but draw-text only had methods for
framebuffer-backend CLOS instances. Added a method on array that sets
cells directly on the framebuffer array, matching make-framebuffer's
return type.

org/framebuffer.org

@@ -356,9 +356,32 @@ does not need (e.g., reverse, dim, blink).
         do (%set-cell fb (+ x i) y (char string i)
                       :fg fg :bg bg
                       :bold bold :italic italic :underline underline
-                      :link-url link-url)))
+                       :link-url link-url)))
 #+END_SRC
 
+*** draw-text (raw array)
+
+Direct rendering onto a raw 2D framebuffer array (the type returned by
+~make-framebuffer~). This lets application code call ~draw-text~ directly on a
+framebuffer without wrapping it in a ~framebuffer-backend~.
+
+#+begin_src lisp :tangle ../src/rendering/framebuffer.lisp
+(defmethod draw-text ((fb array) x y string fg bg
+                      &key bold italic underline reverse dim blink
+                      &allow-other-keys)
+  (declare (ignore reverse dim blink))
+  (let ((h (array-dimension fb 0))
+        (w (array-dimension fb 1)))
+    (loop for i from 0 below (length string)
+          for cx from x
+          while (< cx w)
+          when (and (< y h) (>= cx 0) (>= y 0))
+          do (setf (aref fb y cx)
+                   (make-cell :char (char string i)
+                              :fg fg :bg bg
+                              :bold bold :italic italic :underline underline)))))
+#+end_src
+
 *** draw-rect
 
 Fill a rectangular region with space characters and an optional background