fix: guard process filters against deleted buffers on exit

When Claude Code exits inside a ghostel or eat terminal buffer, the
process filter could fire after the buffer was already killed, causing
"error in process filter: Selecting deleted buffer". Add buffer-live-p
checks before and after orig-filter in both backends.

Author: Kang Tu

ai-code-backends-infra-eat.el

@@ -134,15 +134,18 @@ variables for the terminal process."
           (set-process-filter
            proc
            (lambda (process output)
-             (let ((filtered-output
-                    (with-current-buffer (process-buffer process)
-                      (ai-code-backends-infra--strip-alternate-screen-sequences output))))
-               (when orig-filter
-                 (funcall orig-filter process filtered-output))
-               (with-current-buffer (process-buffer process)
-                 (when (ai-code-backends-infra--output-meaningful-p filtered-output)
-                   (ai-code-backends-infra--note-meaningful-output))
-                 (ai-code-session-link--linkify-recent-output filtered-output)))))))
+             (when-let ((buf (process-buffer process)))
+               (when (buffer-live-p buf)
+                 (let ((filtered-output
+                        (with-current-buffer buf
+                          (ai-code-backends-infra--strip-alternate-screen-sequences output))))
+                   (when orig-filter
+                     (funcall orig-filter process filtered-output))
+                   (when (buffer-live-p buf)
+                     (with-current-buffer buf
+                       (when (ai-code-backends-infra--output-meaningful-p filtered-output)
+                         (ai-code-backends-infra--note-meaningful-output))
+                       (ai-code-session-link--linkify-recent-output filtered-output)))))))))))
       (cons buffer (get-buffer-process buffer)))))
 
 (provide 'ai-code-backends-infra-eat)

ai-code-backends-infra-ghostel.el

@@ -110,12 +110,15 @@ variables for the terminal process."
             (set-process-filter
              proc
              (lambda (process output)
-               (when orig-filter
-                 (funcall orig-filter process output))
-               (with-current-buffer (process-buffer process)
-                 (when (ai-code-backends-infra--output-meaningful-p output)
-                   (ai-code-backends-infra--note-meaningful-output))
-                 (ai-code-session-link--linkify-recent-output output))))))
+               (when-let ((buf (process-buffer process)))
+                 (when (buffer-live-p buf)
+                   (when orig-filter
+                     (funcall orig-filter process output))
+                   (when (buffer-live-p buf)
+                     (with-current-buffer buf
+                       (when (ai-code-backends-infra--output-meaningful-p output)
+                         (ai-code-backends-infra--note-meaningful-output))
+                       (ai-code-session-link--linkify-recent-output output)))))))))
         (cons buffer proc)))))
 
 (provide 'ai-code-backends-infra-ghostel)