Fix Alt+Enter newline not registering on Mac: add Cmd+Enter fallback

macOS's Option key is a compose key (used to type accented/special
characters), which can make it unreliable as a plain modifier in some
browser/layout combinations -- Alt+Enter alone wasn't reaching the handler
for this user on Mac. Microsoft's own Mac Excel shortcut for this is
inconsistent across versions too (Control+Option+Return traditionally,
plain Option+Return only in 365).

- onEditKeydown now accepts Enter with either altKey OR metaKey (Cmd),
  giving a Mac-safe alternative that doesn't depend on Option's compose
  behavior.
- Also checks e.code ('Enter'/'NumpadEnter') alongside e.key, in case
  composition ever alters what .key reports for the combination (.code
  reflects the physical key regardless).

Verified interactively: Alt+Enter, Cmd+Enter, and plain Enter (still
commits normally) all produce the expected value/behavior.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

README.md

@@ -98,7 +98,7 @@ umbenennen, löschen, per Drag sortieren). Zoom 40–200 % pro Blatt
 | `Bild↑` / `Bild↓` | seitenweise (bei festen Tabellen nach Viewport-Höhe) |
 | **`Strg`/`Cmd`+`C`/`X`/`V`** | Kopieren / Ausschneiden / Einfügen (Zellen + Formatierung, bezugsangepasst) |
 | **`F4`** (im Editor/in der Formelleiste) | Bezug am Cursor sperren/zyklisch umschalten: `A1` → `$A$1` → `A$1` → `$A1` → `A1`; bei markiertem Text werden **alle** darin gefundenen Bezüge auf einmal umgeschaltet, jeder ausgehend vom eigenen Zustand |
-| **`Alt`+`Enter`** (im Editor) | Zeilenumbruch in der Zelle einfügen, statt zu committen |
+| **`Alt`+`Enter`** bzw. **`Cmd`+`Enter`** (im Editor) | Zeilenumbruch in der Zelle einfügen, statt zu committen — `Cmd`+`Enter` als Mac-Fallback, da `⌥` (Option) dort eine Compose-Taste ist und nicht überall zuverlässig als reines Modifier ankommt |
 
 Bei **festen (scrollbaren) Tabellen** wird die aktive Zelle bei jeder Navigation
 automatisch in den sichtbaren Bereich gescrollt (unter Beachtung fixierter

src/components/TableGrid.vue

@@ -650,10 +650,16 @@ function cancelEdit() {
   focusRoot();
 }
 function onEditKeydown(e: KeyboardEvent) {
-  if (e.key === 'Enter' && e.altKey) {
+  // Alt+Enter (Windows/Excel-365-Mac) or Cmd+Enter (a macOS-safe fallback --
+  // Option is a compose key there, e.g. for Control+Option+Return, the
+  // traditional Mac Excel shortcut, or some layouts/browsers, so `altKey`
+  // alone isn't fully reliable; `e.code` sidesteps `key` being altered by
+  // that composition, since Enter itself never composes into another char).
+  const isEnter = e.key === 'Enter' || e.code === 'Enter' || e.code === 'NumpadEnter';
+  if (isEnter && (e.altKey || e.metaKey)) {
     // insert a literal newline at the caret ourselves rather than relying on
     // the textarea's native Enter handling, which some browsers/OSes divert
-    // Alt+Enter away from (e.g. as a window/fullscreen shortcut)
+    // this combination away from (e.g. as a window/fullscreen shortcut)
     e.preventDefault();
     e.stopPropagation();
     const el = editInput.value;