Auto-sizing cell editor, multi-ref F4, and Alt+Enter line breaks

1. In-cell editor width/height ("nur in der Breite der Zelle angezeigt"):
   the editor now lives as an overlay (like the clip/fill markers) instead
   of inside its <td>, so it can grow past the cell -- width first, up to
   an approximated display-width cap, then wrapping and growing height.
   Sized via a hidden mirror element (same font/padding, real DOM
   measurement -- a <textarea> can't self-size to content with CSS alone).

2. F4 now cycles every reference a real text selection overlaps, each from
   its own lock state, not just the one at the caret -- select a stretch of
   formula spanning several references and F4 adjusts all of them at once,
   same as Excel. cycleReferenceLock(formula, caret) -> cycleReferenceLocks
   (formula, start, end); a collapsed selection (start === end) keeps the
   old single-reference caret behaviour. Wired into both the in-cell editor
   and the formula bar.

3. Alt+Enter inserts a literal newline in the editor instead of committing
   (explicit splice at the caret, not relying on the textarea's native
   Enter handling, which isn't consistently reachable for Alt+Enter). A
   cell holding a newline displays it wrapped (.cell.multiline) instead of
   collapsing to one ellipsised line.

Along the way: a <td>'s own max-height doesn't cap table-row growth in any
browser (a table-layout quirk) -- a wrapped multi-line cell was silently
growing its row past rowH(r), which would have desynced every pixel
position computed from rowH()/rowTop() (the overlays, sticky frozen panes,
the row-resize handle). Fixed by moving cell text into its own block-level
.cell-content child, which *does* respect max-height + overflow:hidden.

Verified interactively against the dev server with Playwright: a long
formula gets a ~300px editor instead of the 104px cell; Alt+Enter produces
a real "\n" that survives commit and displays wrapped, with the row height
unchanged (26px, not the ~40px it grew to before the .cell-content fix);
F4 on a full-formula selection turns every reference absolute in one press
and keeps cycling all of them on repeated presses; existing selection,
copy/paste and fill-handle behaviour all regression-checked clean.

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

src/engine/refs.ts

@@ -57,34 +57,70 @@ export function toA1(col: number, row: number, colAbs = false, rowAbs = false):
 }
 
 /**
- * Excel/Numbers-style F4: cycle the cell reference at/adjacent to `caret` (a
- * 0-based offset into `formula`, which must start with "=") through
- * relative -> absolute -> row-locked -> column-locked -> relative. Returns
- * the rewritten formula and a caret placed after the toggled reference, or
- * `null` when there's no reference at the caret to toggle.
+ * Excel/Numbers-style F4: cycle every cell reference through
+ * relative -> absolute -> row-locked -> column-locked -> relative, each
+ * from its own current state.
+ *
+ * With a collapsed selection (`selStart === selEnd`, the common case -- just
+ * a caret), this toggles the single reference at/adjacent to it. With a real
+ * text selection, it toggles *every* reference the selection overlaps at
+ * once -- select a stretch of formula text spanning several references and
+ * F4 adjusts them all in one press, same as Excel.
+ *
+ * `selStart`/`selEnd` are 0-based offsets into `formula` (which must start
+ * with "="), i.e. straight from an `<input>`/`<textarea>`'s
+ * `selectionStart`/`selectionEnd`. Returns the rewritten formula and a
+ * selection re-spanning the (possibly resized) references, so a repeated F4
+ * keeps cycling the same ones; `null` when none were found.
  */
-export function cycleReferenceLock(
+export function cycleReferenceLocks(
   formula: string,
-  caret: number,
-): { text: string; caret: number } | null {
+  selStart: number,
+  selEnd: number,
+): { text: string; start: number; end: number } | null {
   if (!formula.startsWith('=')) return null;
   const body = formula.slice(1);
-  const at = caret - 1;
+  const lo = Math.min(selStart, selEnd) - 1;
+  const hi = Math.max(selStart, selEnd) - 1;
+  const collapsed = lo === hi;
   let toks: Token[];
   try {
     toks = tokenize(body);
   } catch {
     return null;
   }
-  const tok = toks.find(
-    (t) => t.type === 'IDENT' && looksLikeCell(t.value) && at >= t.pos && at <= t.pos + t.value.length,
-  );
-  if (!tok) return null;
-  const { col, row, colAbs, rowAbs } = parseA1(tok.value);
-  const [nColAbs, nRowAbs] = nextLock(colAbs, rowAbs);
-  const next = toA1(col, row, nColAbs, nRowAbs);
-  const text = '=' + body.slice(0, tok.pos) + next + body.slice(tok.pos + tok.value.length);
-  return { text, caret: 1 + tok.pos + next.length };
+  const targets: Token[] = [];
+  for (let i = 0; i < toks.length; i++) {
+    const t = toks[i];
+    if (t.type !== 'IDENT' || !looksLikeCell(t.value)) continue;
+    const next = toks[i + 1];
+    if (next && (next.type === 'BANG' || next.type === 'DBLCOLON')) continue; // a table-name qualifier, not a cell
+    const tEnd = t.pos + t.value.length;
+    const hit = collapsed ? lo >= t.pos && lo <= tEnd : t.pos < hi && tEnd > lo;
+    if (hit) targets.push(t);
+  }
+  if (!targets.length) return null;
+
+  let out = '';
+  let last = 0;
+  let start = -1;
+  let end = -1;
+  for (const tok of targets) {
+    const { col, row, colAbs, rowAbs } = parseA1(tok.value);
+    const [nColAbs, nRowAbs] = nextLock(colAbs, rowAbs);
+    const rewritten = toA1(col, row, nColAbs, nRowAbs);
+    out += body.slice(last, tok.pos) + rewritten;
+    if (start === -1) start = out.length - rewritten.length;
+    end = out.length;
+    last = tok.pos + tok.value.length;
+  }
+  out += body.slice(last);
+  // a collapsed caret in -> a collapsed caret out (after the one toggled
+  // reference), same as before; a real selection in keeps spanning every
+  // reference it touched, so a repeated F4 keeps cycling all of them.
+  return collapsed
+    ? { text: '=' + out, start: 1 + end, end: 1 + end }
+    : { text: '=' + out, start: 1 + start, end: 1 + end };
 }
 
 /** A1 -> $A$1 -> A$1 -> $A1 -> A1 -> ... (the classic F4 cycle). */