feat: a table that may not break between rows moves whole

ODF style:may-break-between-rows="false" — probed: LibreOffice leaves four
lines of a page empty rather than split such a table, and splits the identical
one when the attribute says "true". pageBreaks now emits a single atomic leaf
for the wrapper unless the table is taller than a page, where the rule cannot
be met. Imported, exported and round-tripped; Word has no equivalent.

src/lib/editor/extensions/pageBreak.ts

@@ -85,6 +85,21 @@ export const PageBreak = Extension.create({
           },
         },
       },
+      {
+        types: ['table'],
+        attributes: {
+          // ODF style:may-break-between-rows="false": no page break falls between two
+          // of the table's rows, so one too tall for the space left moves whole. A
+          // table taller than a page still breaks — the rule is then unsatisfiable.
+          keepRows: {
+            default: null,
+            parseHTML: (element: HTMLElement) =>
+              element.getAttribute('data-keep-rows') === 'true' ? true : null,
+            renderHTML: (attributes: Record<string, unknown>) =>
+              attributes.keepRows === true ? { 'data-keep-rows': 'true' } : {},
+          },
+        },
+      },
     ];
   },
 

src/lib/editor/extensions/pageBreaks.ts

@@ -652,13 +652,23 @@ export const PageBreaks = Extension.create({
               ? (Array.from(tbody.children) as HTMLElement[])
               : [];
             const realRows = rowEls.filter(r => r.tagName === 'TR' && !r.dataset?.pageBreakSpacer);
+            const spacerHeight = rowEls
+              .filter(r => r.dataset?.pageBreakSpacer)
+              .reduce((sum, r) => sum + r.offsetHeight, 0);
+            // No break may fall between the rows (ODF style:may-break-between-rows), so
+            // the table moves whole — unless it is taller than a page, where the rule
+            // cannot be met and LibreOffice breaks it anyway.
+            const keepRows = tableEl?.dataset?.keepRows === 'true'
+              && wrapperEl.offsetHeight - spacerHeight <= contentHeight;
             // Fallback: no rows found — measure the whole wrapper as one atomic leaf.
-            if (realRows.length === 0) {
+            if (realRows.length === 0 || keepRows) {
+              const top = naturalTopOf(wrapperEl);
+              cumulativeSpacerHeight += spacerHeight;
               leaves.push({
                 el: wrapperEl,
                 kind: 'atomic',
-                naturalTop: naturalTopOf(wrapperEl),
-                naturalHeight: wrapperEl.offsetHeight,
+                naturalTop: top,
+                naturalHeight: wrapperEl.offsetHeight - spacerHeight,
               });
               return;
             }

src/lib/editor/extensions/tableView.ts

@@ -62,6 +62,9 @@ function applyTableStyleAttr(node: PMNode, table: HTMLElement): void {
   const look = node.attrs.tableLook as string | null;
   if (look != null) table.dataset.tableLook = look;
   else delete table.dataset.tableLook;
+  // pageBreaks.ts reads this to keep the table whole (ODF style:may-break-between-rows).
+  if (node.attrs.keepRows === true) table.dataset.keepRows = 'true';
+  else delete table.dataset.keepRows;
 }
 
 // Also bypassed by the node view: the cell margins editor.css reads off the table.