restore: original org-auto-tabularx with inhibit-modification-hooks (worked on Mac1)

Restore the hook-based approach from acb3875 (original working version) + the
inhibit-modification-hooks fix from 457b9d3 that made it work on Emacs 31.

457b9d3 confirmed working by Martin (PDF exported) — only issue was the syntax
warning from the stray paren. This commit has correct paren balance.

Also keep pdf-tools config and corfu-terminal Emacs 31 guard from 98b53cb.

config.el

@@ -325,13 +325,49 @@ Bound to cmd+v in org-mode and markdown-mode."
 ;;; ORG MODE — LATEX EXPORT
 ;;; ============================================================
 
-;; LaTeX table export: use tabularx as default environment.
-;; Org natively supports tabularx: when environment is "tabularx" or "tabulary",
-;; it automatically inserts the required width argument (\linewidth).
-;; No buffer modification, no advice, no filter needed.
-(after! ox-latex
-  (setq org-latex-default-table-environment "tabularx")
-  (add-to-list 'org-latex-packages-alist '("" "tabularx")))
+;; Count data columns in an Org table line
+(defun my/org-count-table-columns (line)
+  "Count the number of data columns in Org table LINE."
+  (length (cl-remove-if
+           (lambda (s) (string-match-p "^-*$" (string-trim s)))
+           (cdr (butlast (split-string line "|"))))))
+
+;; Generate tabularx column spec: first column left-aligned, rest Y (auto-width)
+(defun my/org-table-attr-latex-spec (ncols)
+  "Return tabularx column spec for NCOLS columns: first l, rest Y."
+  (concat "l" (make-string (max 0 (1- ncols)) ?Y)))
+
+;; Automatically insert #+ATTR_LATEX tabularx before tables on LaTeX export.
+;; inhibit-modification-hooks prevents org-element-cache from recursing
+;; during the insert (which caused max-lisp-eval-depth on Emacs 31).
+(defun my/org-auto-tabularx (backend)
+  "Insert #+ATTR_LATEX tabularx before each table when exporting to LaTeX."
+  (when (org-export-derived-backend-p backend 'latex)
+    (let ((inhibit-modification-hooks t))
+      (save-excursion
+        (goto-char (point-min))
+        (while (not (eobp))
+          (cond
+           ((looking-at "^|")
+            (let ((prev-line (save-excursion
+                               (forward-line -1)
+                               (buffer-substring-no-properties
+                                (line-beginning-position) (line-end-position)))))
+              (when (not (string-match-p "^|" prev-line))
+                (when (not (string-match-p "^#\\+ATTR_LATEX" prev-line))
+                  (let* ((table-line (buffer-substring-no-properties
+                                      (line-beginning-position) (line-end-position)))
+                         (ncols (my/org-count-table-columns table-line))
+                         (spec  (my/org-table-attr-latex-spec ncols))
+                         (attr  (format "#+ATTR_LATEX: :environment tabularx :width \\textwidth :align %s\n"
+                                        spec)))
+                    (when (> ncols 0)
+                      (insert attr)))))
+            (forward-line))
+           (t
+            (forward-line)))))))))
+
+(add-hook 'org-export-before-processing-hook #'my/org-auto-tabularx)
 
 ;; Optional: enable booktabs style (horizontal rules in tables)
 ;; (setq org-latex-tables-booktabs t)