fix: disable kitty keyboard, fix CSI parser crashes

- Disabled \033[?u kitty keyboard protocol in modern-backend
  (converts all keys to escape sequences, breaking Ctrl+letter dispatch)
- Fixed parse-csi-sequence: use multiple-value-bind instead of let*
  with destructuring-bind (lost secondary return value from read-param)
- Fixed parse-csi-params format string: pass char-code of terminator
  as distinct argument for ~d, keeping the character for ~C
- Added %query-terminal-size in classes.lisp: ANSI CSI 18t fallback
  for terminal size detection when ioctl fails or returns zero

src/backend/classes.lisp

@@ -1,5 +1,36 @@
 (in-package :cl-tty.backend)
 
+(defun %query-terminal-size ()
+  "Query terminal size via ANSI CSI 18 t and parse the response.
+Returns (values cols rows) or nil."
+  (ignore-errors
+    (let* ((saved (sb-sys:make-fd-stream 0 :input t :buffering :none))
+           (response (make-array 0 :element-type 'character
+                                   :fill-pointer 0 :adjustable t)))
+      (format t "~C[18t" #\Esc)
+      (force-output)
+      (loop with deadline = (+ (get-internal-real-time)
+                               (* internal-time-units-per-second 0.2))
+            while (< (get-internal-real-time) deadline)
+            do (let ((ch (read-char-no-hang saved nil nil)))
+                 (when ch
+                   (vector-push-extend ch response)
+                   (when (char= ch #\t) (return)))))
+      (when (>= (length response) 8)
+        (let* ((str (subseq response 1))
+               (start (or (position #\[ str) 0))
+               (after (subseq str (1+ start)))
+               (semi (position #\; after)))
+          (when semi
+            (let* ((cols-start (1+ semi))
+                   (cols-end (position #\t after :start cols-start))
+                   (rows (parse-integer (subseq after 0 semi) :junk-allowed t))
+                   (cols (when cols-end
+                           (parse-integer (subseq after cols-start cols-end)
+                                          :junk-allowed t))))
+              (when (and rows cols (> rows 0) (> cols 0))
+                (values cols rows)))))))))
+
 (defclass backend () ())
 
 (defgeneric initialize-backend (backend)