fix: set both dimensions from stty, add tput fallback, export shell vars

- stty size returns 'rows cols'. Old code set only one dimension
  when both env vars were missing; new code sets both.
- Added tput cols/lines as final env-var fallback for systems
  where COLUMNS/LINES are not exported and stty is unavailable.
- Added 'export COLUMNS LINES' to the passepartout script so
  SBCL can read them from the environment.

src/backend/simple.lisp

@@ -46,10 +46,21 @@
                    (parts (and out (uiop:split-string
                                      (string-trim '(#\newline #\space) out)))))
               (when (and parts (= (length parts) 2))
-                (let ((a (parse-integer (first parts) :junk-allowed t))
-                      (b (parse-integer (second parts) :junk-allowed t)))
-                  (when (and a b (> a 0) (> b 0))
-                    (if cols (setf rows b) (setf cols a)))))))
+                (let ((stty-rows (parse-integer (first parts) :junk-allowed t))
+                      (stty-cols (parse-integer (second parts) :junk-allowed t)))
+                  (when (and stty-rows stty-cols (> stty-rows 0) (> stty-cols 0))
+                    (unless cols (setf cols stty-cols))
+                    (unless rows (setf rows stty-rows)))))))
+          (unless (and cols rows)
+            (let ((out (uiop:run-program '("sh" "-c" "tput cols 2>/dev/null; tput lines 2>/dev/null")
+                                          :output :string
+                                          :ignore-error-status t)))
+              (when out
+                (let* ((parts (uiop:split-string (string-trim '(#\newline #\space) out)))
+                       (a (when parts (parse-integer (first parts) :junk-allowed t)))
+                       (b (when (cdr parts) (parse-integer (second parts) :junk-allowed t))))
+                  (when a (setf cols a))
+                  (when b (setf rows b))))))
           (when (and cols rows (> cols 0) (> rows 0))
             (values cols rows))))
       (values 80 24)))