macos: fix mouse — scroll wheel works, movement doesn't move cursor

- mouse-autoselect-window nil: mouse movement no longer switches
  active window (was the main cause of apparent cursor jumping)
- focus-follows-mouse nil: same — no focus change on hover
- mouse clicks still disabled ([mouse-1..3] → #'ignore)
- scroll wheel explicitly configured: 3 lines/tick, no acceleration,
  no progressive speed (mouse-wheel-scroll-amount)

config.el

@@ -54,8 +54,8 @@
 ;;; MACOS / PLATFORM
 ;;; ============================================================
 
-(setq mouse-autoselect-window t
-      focus-follows-mouse t
+(setq mouse-autoselect-window nil   ; don't switch window on mouse move
+      focus-follows-mouse nil        ; don't change focus on mouse move
       select-enable-clipboard t
       select-enable-primary t
       inhibit-splash-screen t)
@@ -168,6 +168,8 @@ Bound to cmd+v in org-mode and markdown-mode."
         mac-right-option-modifier 'none))
 
 ;; Fix C: Disable mouse clicks in GUI Emacs (prevent accidental cursor movement)
+;; Scroll wheel ([wheel-up/down]) is intentionally NOT disabled — scrolling works.
+;; Mouse movement does not move cursor (mouse-autoselect-window nil above).
 (when (display-graphic-p)
   (dolist (key '([mouse-1] [mouse-2] [mouse-3]
                  [double-mouse-1] [double-mouse-2] [double-mouse-3]
@@ -175,7 +177,11 @@ Bound to cmd+v in org-mode and markdown-mode."
                  [drag-mouse-1] [drag-mouse-2] [drag-mouse-3]
                  [down-mouse-1] [down-mouse-2] [down-mouse-3]))
     (global-set-key key #'ignore))
-  (setq mouse-highlight nil))
+  (setq mouse-highlight nil)
+  ;; Smooth scroll wheel: 3 lines per tick, no acceleration
+  (setq mouse-wheel-scroll-amount '(3 ((shift) . 1) ((control) . nil))
+        mouse-wheel-progressive-speed nil
+        mouse-wheel-follow-mouse t))