Revert overflow detection — keep only viewport pinning

The pos-visible-in-window-p based overflow detection caused multiple
issues: it broke mouse scrolling by resetting the viewport position
during terminal resize, and interacted badly with Emacs display state
(horizontal scroll, font size changes).

Remove all overflow detection code (ghostel--check-overflow,
ghostel--height-adjustment).  Keep the simple set-window-start pin
which fixes the main issue (viewport drift with TUI apps like Claude
Code).

The emoji line-height issue remains open for a future fix using a
different approach.

Author: dakra

ghostel.el

@@ -548,8 +548,7 @@ DIR is the module directory."
 (defvar-local ghostel--resize-timer nil
   "Timer for debounced SIGWINCH on alt screen.")
 
-(defvar-local ghostel--height-adjustment 0
-  "Rows subtracted from window-body-height to fit tall lines (emoji).")
+
 
 
 (defvar-local ghostel--last-directory nil
@@ -1715,26 +1714,10 @@ frame after idle to improve interactive responsiveness."
             (ghostel--pin-window-start)))))))
 
 (defun ghostel--pin-window-start ()
-  "Pin the window so terminal row 1 stays at the top.
-When tall glyphs (emoji) cause content to overflow the window,
-shrink the terminal by one row and re-render."
+  "Pin the window so terminal row 1 stays at the top."
   (let ((win (get-buffer-window)))
     (when win
-      (set-window-start win (point-min))
-      (when (and ghostel--term
-                 (> (point-max) (point-min))
-                 (not (pos-visible-in-window-p (1- (point-max)) win)))
-        ;; Content overflows — reduce terminal by one row.
-        (cl-incf ghostel--height-adjustment)
-        (let* ((height (- (window-body-height win)
-                          ghostel--height-adjustment))
-               (width (window-max-chars-per-line win)))
-          (when (> height 0)
-            (ghostel--set-size ghostel--term height width)
-            (when (and ghostel--process (process-live-p ghostel--process))
-              (set-process-window-size ghostel--process height width))
-            (ghostel--redraw ghostel--term ghostel-full-redraw)
-            (set-window-start win (point-min))))))))
+      (set-window-start win (point-min)))))
 
 (defun ghostel-force-redraw ()
   "Force a full terminal redraw (for debugging)."
@@ -1753,7 +1736,6 @@ PROCESS is the shell process, WINDOWS is the list of windows."
   (let* ((window (car windows))
          (width (window-max-chars-per-line window))
          (height (window-body-height window)))
-    (setq ghostel--height-adjustment 0)
     (when ghostel--term
       (if (ghostel--mode-enabled ghostel--term 1049)
           ;; Alt screen: debounce the entire resize (terminal + SIGWINCH)