Show the selected range, not just the active cell, in status/formula bar

New store computed selectionRangeName: for a single cell it's identical
to activeCellName ("Umsatz::B2"), for a multi-cell selection it shows
the full primary rectangle ("Umsatz::B2:E6"), and a discontiguous
multi-selection gets a "+N" suffix for the further rectangles.
activeCellName itself is untouched (still anchor-only, since that's what
a formula/edit actually targets) -- only the formula bar's name field and
the status bar's range label switch to the new computed.

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

src/store/document.ts

@@ -1412,6 +1412,28 @@ function createStore() {
     return `${t?.name ?? '—'}::${toA1(cell.col, cell.row)}`;
   });
 
+  /** Like {@link activeCellName}, but for a multi-cell selection it shows the
+   *  full range (`Umsatz::B2:E6`) instead of just the anchor -- used wherever
+   *  the UI shows "where am I" (formula bar, status bar), as opposed to
+   *  `activeCellName`/`activeCell`, which stay anchor-only because that's
+   *  what a formula/edit actually targets (see the "selection aggregate &
+   *  cell name are live" test). A discontiguous multi-selection additionally
+   *  gets a `+N` suffix for the further rectangles beyond the primary one. */
+  const selectionRangeName = computed(() => {
+    const sel = doc.selection;
+    const t = sel ? tableById(sel.tableId) : activeTable.value;
+    const tableName = t?.name ?? '—';
+    if (!sel) return `${tableName}::${toA1(0, 0)}`;
+    const rects = selectionRects(sel);
+    const [p] = rects;
+    const addr =
+      p.c0 === p.c1 && p.r0 === p.r1
+        ? toA1(p.c0, p.r0)
+        : `${toA1(p.c0, p.r0)}:${toA1(p.c1, p.r1)}`;
+    const extra = rects.length > 1 ? ` +${rects.length - 1}` : '';
+    return `${tableName}::${addr}${extra}`;
+  });
+
   const activeCellInput = computed(() => {
     const sel = doc.selection;
     return sel ? cellInput(sel.tableId, sel.anchor.col, sel.anchor.row) : '';
@@ -1606,6 +1628,7 @@ function createStore() {
     selectionRects,
     activeCell,
     activeCellName,
+    selectionRangeName,
     activeCellInput,
     selectionAggregate,
     // clipboard