fix(formatters): prevent backticks in exception values and stack frames from breaking code spans

- markdown.ts safeCodeSpan: also replace ` with ˋ (U+02CB MODIFIER LETTER
  GRAVE ACCENT) — visually identical in monospace but never a code-span
  delimiter. Prevents JS exception messages like 'Unexpected token `' from
  prematurely closing the backtick-delimited code span.
- human.ts formatStackFrameMarkdown: use safeCodeSpan() for the full
  'at fn (file:line:col)' string instead of raw template-literal backticks
- human.ts formatExceptionValueMarkdown: use safeCodeSpan() for the
  'type: value' header instead of raw backticks

Author: BYK

src/lib/formatters/human.ts

@@ -718,7 +718,7 @@ function formatStackFrameMarkdown(frame: StackFrame): string {
   const col = frame.colNo ?? "?";
   const inAppTag = frame.inApp ? " `[in-app]`" : "";
 
-  lines.push(`\`at ${fn} (${file}:${line}:${col})\`${inAppTag}`);
+  lines.push(`${safeCodeSpan(`at ${fn} (${file}:${line}:${col})`)}${inAppTag}`);
 
   if (frame.context && frame.context.length > 0) {
     lines.push("");
@@ -743,7 +743,7 @@ function formatExceptionValueMarkdown(exception: ExceptionValue): string {
 
   const type = exception.type || "Error";
   const value = exception.value || "";
-  lines.push(`**\`${type}: ${value}\`**`);
+  lines.push(`**${safeCodeSpan(`${type}: ${value}`)}**`);
 
   if (exception.mechanism) {
     const handled = exception.mechanism.handled ? "handled" : "unhandled";

src/lib/formatters/markdown.ts

@@ -203,22 +203,26 @@ export function mdRow(cells: readonly string[]): string {
 }
 
 /**
- * Wrap a user-supplied string in a backtick code span for use inside a
- * markdown table cell.
+ * Wrap a user-supplied string in a backtick code span.
  *
  * Inside a CommonMark code span, backslashes are **literal** (not escape
- * characters), so `\|` would render as `\|` rather than protecting the
- * table delimiter. Instead this helper:
- *
- * - Replaces `|` with `│` (U+2502, BOX DRAWINGS LIGHT VERTICAL) — visually
- *   identical but not a markdown table delimiter.
- * - Replaces newlines with a space — code spans cannot span lines.
+ * characters), so backslash-based escaping of special characters does not
+ * work. This helper sanitises the three characters that would otherwise break
+ * the span or the surrounding table structure:
+ *
+ * - Replaces `` ` `` with `ˋ` (U+02CB MODIFIER LETTER GRAVE ACCENT) —
+ *   visually identical in monospace fonts but never treated as a code-span
+ *   delimiter. Prevents exception messages like `Unexpected token \`` from
+ *   prematurely closing the span.
+ * - Replaces `|` with `│` (U+2502 BOX DRAWINGS LIGHT VERTICAL) — prevents
+ *   table column splitting when used inside a markdown table cell.
+ * - Replaces newlines with a space — code spans cannot span multiple lines.
  *
  * @param value - Raw string to format as a code span
- * @returns `` `value` `` with pipe and newline characters sanitised
+ * @returns `` `value` `` with backtick, pipe, and newline characters sanitised
  */
 export function safeCodeSpan(value: string): string {
-  return `\`${value.replace(/\|/g, "│").replace(/\n/g, " ")}\``;
+  return `\`${value.replace(/`/g, "ˋ").replace(/\|/g, "│").replace(/\n/g, " ")}\``;
 }
 
 /**