prosemirror-tables already ships mergeCells/splitCell and the schema
(tableNodes) already carries colspan/rowspan -- only the controls were
missing. Adds the two commands, toolbar buttons whose enabled state
follows the selection (merge needs a multi-cell selection, split a
merged cell), and de+en labels.
Both render paths now carry the spans: docToHtml emits colspan/rowspan
(read mode, exports via the HTML path), and the markdown serializer pads
a colspan with empty cells so every row keeps the table's column count
-- rowspan stays lossy there, GFM cannot express it.
e2e drives merge and split through the toolbar; the cell selection is
made per Shift+Click because a keypress in the same tick as the
preceding click races the editor's post-click rendering (keyboard cell
selection itself works, verified interactively with a settled editor).
Closes#337
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012aoPvnakfBP28nAfijgUY9
Claude Fable 5
d76c731473