v0.3.3: left/right cursor movement in input

Adds :cursor-pos to TUI state. New functions:
- input-insert-char(ch): insert at cursor position, advance cursor
- input-delete-char(): delete char before cursor (standard backspace)

on-key handlers:
- Left arrow: decrement cursor-pos (clamped >= 0)
- Right arrow: increment cursor-pos (clamped <= buffer-len)
- Character input: input-insert-char at cursor position
- Backspace: input-delete-char at cursor position
- Enter: reset cursor-pos to 0

view-input: cursor at visual position matching cursor-pos

Test: (init-state) → (input-insert-char #\h) → (input-insert-char #\i)
→ (setf cursor-pos 1) → (input-insert-char #\X) → 'hXi' at pos 2

lisp/gateway-tui-main.lisp

@@ -94,8 +94,9 @@
                    (setf (st :busy) t)
                    (send-daemon (list :type :event
                                      :payload (list :sensor :user-input :text text)))))
-                (setf (st :input-buffer) nil)
-                (setf (st :dirty) (list t t t))))))
+                 (setf (st :input-buffer) nil)
+                 (setf (st :cursor-pos) 0)
+                 (setf (st :dirty) (list t t t))))))
        ;; Tab — command completion
        ((or (eql ch 9) (eq ch :tab))
         (let ((text (input-string)))
@@ -110,11 +111,21 @@
                 (when (member match '("/eval" "/focus" "/scope") :test #'string=)
                   (push #\Space (st :input-buffer)))
                 (setf (st :dirty) (list nil nil t)))))))
-       ;; Backspace
-       ((or (eq ch :backspace) (eql ch 127) (eql ch 8)
-            (eql ch #\Backspace))
-       (when (st :input-buffer) (pop (st :input-buffer)))
-       (setf (st :dirty) (list nil nil t)))
+        ;; Backspace
+        ((or (eq ch :backspace) (eql ch 127) (eql ch 8)
+             (eql ch #\Backspace))
+        (input-delete-char)
+        (setf (st :dirty) (list nil nil t)))
+       ;; Left arrow
+       ((or (eq ch :left) (eql ch 260))
+        (when (> (or (st :cursor-pos) 0) 0)
+          (decf (st :cursor-pos))
+          (setf (st :dirty) (list nil nil t))))
+       ;; Right arrow
+       ((or (eq ch :right) (eql ch 261))
+        (when (< (or (st :cursor-pos) 0) (length (st :input-buffer)))
+          (incf (st :cursor-pos))
+          (setf (st :dirty) (list nil nil t))))
       ;; Up arrow
       ((or (eq ch :up) (eql ch 259))
        (let* ((h (st :input-history)) (p (st :input-hpos)))
@@ -141,15 +152,15 @@
       ((or (eq ch :npage) (eql ch 338))
        (setf (st :scroll-offset) (max 0 (- (st :scroll-offset) 5)))
        (setf (st :dirty) (list nil t nil)))
-      ;; Printable
-      (t
-       (let ((chr (typecase ch
-                    (character ch)
-                    (integer (code-char ch))
-                    (t nil))))
-         (when (and chr (graphic-char-p chr))
-           (push chr (st :input-buffer))
-           (setf (st :dirty) (list nil nil t))))))))
+       ;; Printable
+       (t
+        (let ((chr (typecase ch
+                     (character ch)
+                     (integer (code-char ch))
+                     (t nil))))
+          (when (and chr (graphic-char-p chr))
+            (input-insert-char chr)
+            (setf (st :dirty) (list nil nil t))))))))
 
 (defun on-daemon-msg (msg)
   (let* ((payload (getf msg :payload))