feat: initial support for multi-column; lists and media fixes(Copy/paste project)

[VladaHarbour]

This PR introduces fixes to support copy/paste experience within Superdoc:

1. Preserves multi-column layout
2. Preserves lists (including nested)
3. Preserves images and headings

(We have hyperlinks and table support in current stable version)

[linear]

SD-148 Feature: Preserve formatting when copying from SuperDoc and pasting into SuperDoc

[chatgpt-codex-connector]

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Reviewed commit: 547bdff47c

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[caio-pizzol]

@VladaHarbour nice work, Codex bot comments from earlier are all handled.

• handleCutEvent: preventDefault before the try block means Cmd+X silently fails if anything throws — see inline fix
• stripWordListConditionalPrefixes: missing [endif] eats all content after it — see inline warning
• createListIdAllocator is copy-pasted between two files, bodySectPr helpers are duplicated — see inline suggestions
• missing round-trip tests for embedSliceInHtml/extractSliceFromHtml/stripSliceFromHtml and shouldPreserveSlicePastedListRendering
• no Playwright tests for copy-paste yet — fine as follow-up

[caio-pizzol]

if anything inside the try block fails, preventDefault already blocked the browser's cut — so the user presses Cmd+X and nothing happens (no clipboard data, no deletion). moving preventDefault to after the clipboard writes means the browser's own cut kicks in as a fallback.

Suggested change

	try {
	const slice = view.state.doc.slice(from, to);
	const fragment = slice.content;
	const sliceJson = JSON.stringify(slice.toJSON());
	clipboardData.setData(SUPERDOC_SLICE_MIME, sliceJson);
	const mediaJson = collectReferencedImageMediaForClipboard(sliceJson, editor);
	if (mediaJson) {
	clipboardData.setData(SUPERDOC_MEDIA_MIME, mediaJson);
	}
	const div = document.createElement('div');
	const serializer = PmDOMSerializer.fromSchema(view.state.schema);
	div.appendChild(serializer.serializeFragment(fragment));
	annotateFragmentDomWithClipboardData(div, fragment, editor);
	const html = unflattenListsInHtml(div.innerHTML);
	const bodySectPr = view.state.doc.attrs?.bodySectPr;
	const bodySectPrJson = bodySectPr && bodySectPrShouldEmbed(bodySectPr) ? JSON.stringify(bodySectPr) : '';
	clipboardData.setData('text/html', embedSliceInHtml(html, sliceJson, bodySectPrJson));
	clipboardData.setData('text/plain', fragment.textBetween(0, fragment.size, '\n\n'));
	event.preventDefault();
	view.dispatch(view.state.tr.deleteSelection().scrollIntoView());
	} catch (error) {
	console.warn('Failed to handle cut:', error);
	}

[VladaHarbour]

moved preventDefault inside try/catch

[caio-pizzol]

if the closing [endif] comment is missing (broken Word HTML), this loop removes every node after it until there's nothing left. a warning would make this easier to debug:

Suggested change

	while (j < node.childNodes.length) {
	while (j < node.childNodes.length) {
	const next = node.childNodes[j];
	if (next?.nodeType === Node.COMMENT_NODE && next.nodeValue?.includes('[endif]')) {
	node.removeChild(next);
	break;
	}
	node.removeChild(next);
	}
	if (j >= node.childNodes.length) {
	console.warn('[SuperDoc] stripWordListConditionalPrefixes: missing [endif], some content may have been removed');
	}

[VladaHarbour]

created more advanced handling for this corner case + test

[caio-pizzol]

tryApplyEmbeddedBodySectPr and applyEmbeddedBodySectPrToTransaction do the same checks and the same work — only difference is who owns the transaction. could be one shared function:

function applyBodySectPrToTr(editor, tr, bodySectPr, currentDoc) {
  if (!bodySectPr || typeof bodySectPr !== 'object') return false;
  const incomingCols = getSectPrColumns(bodySectPr);
  if (!incomingCols?.count || incomingCols.count <= 1) return false;
  const currentCols = getSectPrColumns(currentDoc.attrs?.bodySectPr);
  if (currentCols?.count > 1) return false;
  const clone = JSON.parse(JSON.stringify(bodySectPr));
  tr.setDocAttribute('bodySectPr', clone);
  if (editor?.converter) editor.converter.bodySectPr = clone;
  return true;
}

worth doing?

[caio-pizzol]

createListIdAllocator is identical to the one in html-helpers.js:53 — moving it to the shared numbering helpers would keep them from drifting apart.

[caio-pizzol]

same createListIdAllocator as InputRule.js:790 — see comment there.