fix: markdown tables drop empty cells and misalign columns (#1164)

* refactor: extract splitTableRow helper for markdown tables

* fix: keep empty interior cells in markdown tables to preserve columns

* test: splitTableRow keeps empty interior cells

static/js/markdown/tableRow.js

@@ -0,0 +1,18 @@
+// static/js/markdown/tableRow.js
+//
+// Pure helper for splitting a markdown table row into cells. No DOM —
+// safe to import anywhere and to unit-test under node.
+
+// Split a "| a | b | c |" row into trimmed cell strings.
+//
+// Strip only the optional leading/trailing pipe, then split — filtering out
+// every empty cell (the old behaviour) dropped intentionally-empty interior
+// cells too, so "| a |  | c |" collapsed to 2 columns and misaligned with the
+// header.
+export function splitTableRow(row) {
+  return (row || '')
+    .replace(/^\s*\|/, '')
+    .replace(/\|\s*$/, '')
+    .split('|')
+    .map((cell) => cell.trim());
+}