fix(table): escape pipe chars in cells on serialize, unescape on parse

- escapeCell() replaces unescaped | with \| before writing each cell,
  applied in both width calculation and formatRow so padding is accurate
- parseRow unescapes \| back to | after splitting on unescaped pipes
- Adds round-trip regression test for cells containing pipe characters

Addresses coderabbitai review comment on PR #5680.

web/src/utils/markdown-table.test.ts

@@ -138,6 +138,18 @@ describe("serializeMarkdownTable", () => {
     expect(new Set(lines.map((l) => l.length)).size).toBe(1);
   });
 
+  it("round-trips a cell containing a pipe character", () => {
+    const data: TableData = {
+      headers: ["A", "B"],
+      rows: [["foo|bar", "baz"]],
+      alignments: ["none", "none"],
+    };
+    const md = serializeMarkdownTable(data);
+    const parsed = parseMarkdownTable(md);
+    expect(parsed?.rows[0][0]).toBe("foo|bar");
+    expect(parsed?.rows[0][1]).toBe("baz");
+  });
+
   it("round-trips through parse and serialize", () => {
     const original = `| Name  | Age |
 | ----- | --- |

web/src/utils/markdown-table.ts

@@ -41,7 +41,7 @@ export function parseMarkdownTable(md: string): TableData | null {
     let trimmed = line;
     if (trimmed.startsWith("|")) trimmed = trimmed.slice(1);
     if (trimmed.endsWith("|")) trimmed = trimmed.slice(0, -1);
-    return trimmed.split(/(?<!\\)\|/).map((cell) => cell.trim());
+    return trimmed.split(/(?<!\\)\|/).map((cell) => cell.trim().replace(/\\\|/g, "|"));
   };
 
   const headers = parseRow(lines[0]);
@@ -84,12 +84,14 @@ export function serializeMarkdownTable(data: TableData): string {
   const { headers, rows, alignments } = data;
   const colCount = headers.length;
 
+  const escapeCell = (text: string): string => text.replace(/(?<!\\)\|/g, "\\|");
+
   // Calculate maximum width per column (minimum 3 for the separator).
   const widths: number[] = [];
   for (let c = 0; c < colCount; c++) {
-    let max = Math.max(3, headers[c].length);
+    let max = Math.max(3, escapeCell(headers[c]).length);
     for (const row of rows) {
-      max = Math.max(max, (row[c] || "").length);
+      max = Math.max(max, escapeCell(row[c] || "").length);
     }
     widths.push(max);
   }
@@ -110,7 +112,7 @@ export function serializeMarkdownTable(data: TableData): string {
   const formatRow = (cells: string[]): string => {
     const formatted = cells.map((cell, i) => {
       const align = alignments[i] || "none";
-      return padCell(cell, widths[i], align);
+      return padCell(escapeCell(cell), widths[i], align);
     });
     return "| " + formatted.join(" | ") + " |";
   };