Size PTY against the buffer window, not the selected one

`ghostel--start-process' recomputed the PTY rows/cols from
`(window-body-height)' / `(window-max-chars-per-line)' with no
window argument, i.e. against the *selected* window.
`ghostel--init-buffer' had just sized the libghostty terminal
against the *buffer's* window.  When the two are different
(popup display rules that don't select the popup, side windows,
etc.) the PTY and the libghostty terminal start out disagreeing,
and no SIGWINCH ever fires to reconcile them — alt-screen apps
like Claude Code's /tui fullscreen lay out against the wrong
size and the bottom rows look "visually collapsed" until the
user resizes the frame (#192).

Read the dims from `ghostel--term-rows' / `ghostel--term-cols'
that `ghostel--init-buffer' (the only caller) just set, so the
PTY and the libghostty terminal are guaranteed to match by
construction.

Author: dakra

lisp/ghostel.el

@@ -2960,8 +2960,14 @@ matches the PTY window size, and stores the process in
   "Start the shell process with a PTY.
 When `default-directory' is a remote TRAMP path, spawn the shell
 on the remote host."
-  (let* ((height (max 1 (window-body-height)))
-         (width (max 1 (window-max-chars-per-line)))
+  ;; Read dims from the buffer-locals set by `ghostel--init-buffer'
+  ;; (the only caller).  Recomputing from `(window-body-height)' here
+  ;; would query the *selected* window, which can differ from the
+  ;; buffer's window when the buffer is shown in a popup that didn't
+  ;; get selected — leaving the PTY and the libghostty terminal sized
+  ;; against different windows (issue #192).
+  (let* ((height (max 1 ghostel--term-rows))
+         (width (max 1 ghostel--term-cols))
          (remote-p (file-remote-p default-directory))
          (shell (ghostel--get-shell))
          (ghostel-dir (ghostel--resource-root))

test/ghostel-test.el

@@ -6942,15 +6942,15 @@ internal `TERM=xterm-ghostty' so a `process-environment' lookup (which
 returns the first match) resolves to the user's value."
   (let ((captured-env nil)
         (orig-make-process (symbol-function #'make-process)))
-    (cl-letf (((symbol-function #'window-body-height)
-               (lambda (&optional _w) 25))
-              ((symbol-function #'window-max-chars-per-line)
-               (lambda (&optional _w) 80))
-              ((symbol-function #'make-process)
+    (cl-letf (((symbol-function #'make-process)
                (lambda (&rest plist)
                  (setq captured-env process-environment)
                  (apply orig-make-process plist))))
       (with-temp-buffer
+        ;; `ghostel--start-process' reads dims from these buffer-locals
+        ;; (set by `ghostel--init-buffer' in the real flow).
+        (setq-local ghostel--term-rows 25
+                    ghostel--term-cols 80)
         (let* ((process-environment '("PATH=/usr/bin:/bin" "HOME=/tmp"))
                (ghostel-shell "/bin/sh")
                (ghostel-shell-integration nil)