fix(mobile): two more table parsers hold a pipe in a cell (OTA phase C follow-up) (#22114)

* test(mobile): pin escaped pipes in mobile markdown table cells

The mobile preview parser splits a table row on every pipe, so a cell
that escaped one becomes two cells and keeps the backslash.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

* fix(mobile): read table rows through the shared row splitter

The editor's markdown-table-rows already splits on unescaped pipes only
and unescapes the cell; it has no imports of its own, so owning the rule
once costs the preview parser nothing.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

* test(mobile): pin escaped-pipe rows in PR comment tables

Its splitter strips the trailing pipe before walking escapes and reads
`\\|` as an escaped pipe, so a row ending in `\|` loses the pipe and a
cell holding a backslash swallows the separator after it.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

* fix(mobile): split PR comment table rows on unescaped pipes only

Its own delimiter grammar stays local: a single dash still opens a table
here, which the editor's three-dash separator would reject.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

* test(config): repin the session route closure at 4,332 modules

markdown-table-rows.ts joins through the PR comment renderer. Measured on
this head: 4,332 modules / 990 local, and it is the only file under
rich-markdown/ in the closure, so nothing came with it.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

config/scripts/mobile-web-app-session-terminal-closure.test.mjs

@@ -229,8 +229,16 @@ const MERMAID_PACKAGE = 'node_modules/mermaid/'
  * diffed to name the difference: those two leave and nothing joins. The same measurement, taken
  * before #22067 landed, is how this branch read main's pin of 4,330 as three modules stale — the
  * three the paragraph above names.
+ *
+ * Then the two other table parsers gave up their own row splitters and read the editor's
+ * `src/components/rich-markdown/markdown-table-rows.ts` instead, which the session page reaches
+ * through the PR comment renderer. It is the one module that joins, and the only one it can be: it
+ * imports nothing, and no other file under `rich-markdown/` is in the closure beside it.
+ *
+ *   modules        4331 -> 4332   (+1)
+ *   local modules   989 ->  990   (+1)
  */
-const SESSION_ROUTE_MODULES = 4331
+const SESSION_ROUTE_MODULES = 4332
 
 /** What the page enters this route through once the route is a switch with a `.web.tsx` sibling. */
 const ROUTE_ENTRY = [

mobile/src/components/MobileMarkdown.test.ts

@@ -45,6 +45,26 @@ describe('parseMobileMarkdown', () => {
     ])
   })
 
+  it('keeps an escaped pipe inside the cell that escaped it', () => {
+    expect(parseMobileMarkdown('| Cmd | Note |\n| --- | --- |\n| a \\| b | c |')).toEqual([
+      {
+        type: 'table',
+        headers: ['Cmd', 'Note'],
+        rows: [['a | b', 'c']]
+      }
+    ])
+  })
+
+  it('ends a cell at the pipe following an escaped backslash', () => {
+    expect(parseMobileMarkdown('| A | B |\n| --- | --- |\n| x\\\\|y |')).toEqual([
+      {
+        type: 'table',
+        headers: ['A', 'B'],
+        rows: [['x\\', 'y']]
+      }
+    ])
+  })
+
   it('parses standalone HTTPS images without folding them into paragraphs', () => {
     expect(parseMobileMarkdown('![Screenshot](https://example.com/screen.png)')).toEqual([
       {

mobile/src/components/mobile-markdown-parser.ts

@@ -1,3 +1,5 @@
+import { isTableSeparator, splitTableRow } from './rich-markdown/markdown-table-rows'
+
 export type MobileMarkdownBlock =
   | { type: 'paragraph'; text: string }
   | { type: 'heading'; level: number; text: string }
@@ -11,20 +13,6 @@ export type MobileMarkdownBlock =
 const HEADING = /^(#{1,6})\s+(.+)$/
 const CODE_FENCE = /^```([A-Za-z0-9_-]+)?\s*$/
 
-function splitTableRow(line: string): string[] {
-  return line
-    .trim()
-    .replace(/^\|/, '')
-    .replace(/\|$/, '')
-    .split('|')
-    .map((cell) => cell.trim())
-}
-
-function isTableSeparator(line: string): boolean {
-  const cells = splitTableRow(line)
-  return cells.length > 0 && cells.every((cell) => /^:?-{3,}:?$/.test(cell))
-}
-
 export function parseMobileMarkdown(content: string): MobileMarkdownBlock[] {
   const lines = content.replace(/\r\n?/g, '\n').split('\n')
   const blocks: MobileMarkdownBlock[] = []

mobile/src/components/pr-sidebar/markdown-blocks.test.ts

@@ -135,6 +135,30 @@ describe('parseMarkdownBlocks tables', () => {
     ])
   })
 
+  it('keeps an escaped pipe that ends a row carrying no closing pipe', () => {
+    const md = ['A | B', '--- | ---', 'x | y \\|'].join('\n')
+    expect(parseMarkdownBlocks(md)).toEqual([
+      {
+        kind: 'table',
+        headers: ['A', 'B'],
+        align: ['left', 'left'],
+        rows: [['x', 'y |']]
+      }
+    ])
+  })
+
+  it('ends a cell at the pipe following an escaped backslash', () => {
+    const md = ['| A | B |', '| --- | --- |', '| x\\\\|y |'].join('\n')
+    expect(parseMarkdownBlocks(md)).toEqual([
+      {
+        kind: 'table',
+        headers: ['A', 'B'],
+        align: ['left', 'left'],
+        rows: [['x\\', 'y']]
+      }
+    ])
+  })
+
   it('does not treat prose containing a pipe as a table (no delimiter row)', () => {
     expect(parseMarkdownBlocks('this | that is just text')).toEqual([
       { kind: 'paragraph', text: 'this | that is just text' }

mobile/src/components/pr-sidebar/markdown-blocks.ts

@@ -1,4 +1,5 @@
 import { createMarkdownInlineMatcher } from '../markdown-inline-matcher'
+import { splitTableRow } from '../rich-markdown/markdown-table-rows'
 
 // Tiny, dependency-free markdown model for PR comment bodies. We render GitHub
 // markdown without a third-party RN markdown library (the previous dependency hung
@@ -194,36 +195,7 @@ function parseLines(content: string): MarkdownBlock[] {
   return blocks
 }
 
-// Splits a `| a | b |` table row into trimmed cells. Tolerates missing outer
-// pipes and escaped `\|` inside cells. Total: never throws on odd input.
-function splitTableRow(line: string): string[] {
-  const cells: string[] = []
-  let cell = ''
-  let trimmed = line.trim()
-  if (trimmed.startsWith('|')) {
-    trimmed = trimmed.slice(1)
-  }
-  if (trimmed.endsWith('|')) {
-    trimmed = trimmed.slice(0, -1)
-  }
-  for (let j = 0; j < trimmed.length; j += 1) {
-    const ch = trimmed[j]
-    if (ch === '\\' && trimmed[j + 1] === '|') {
-      cell += '|'
-      j += 1
-      continue
-    }
-    if (ch === '|') {
-      cells.push(cell.trim())
-      cell = ''
-      continue
-    }
-    cell += ch
-  }
-  cells.push(cell.trim())
-  return cells
-}
-
+// A single dash is a delimiter cell here, unlike the editor's three-dash separator.
 function isTableDelimiter(line: string): boolean {
   return splitTableRow(line).every((cell) => /^:?-+:?$/.test(cell))
 }