fix: restore try-catch around BigInt conversion in unixNanoToDateTime

BigInt(text) throws SyntaxError for non-integer strings (e.g. '12.34',
'abc'). Since this function processes external OTLP trace data, malformed
input is realistic and callers have no surrounding error handling. Wrap
the conversion in try-catch to gracefully return null on invalid input.

Author: cursoragent

apps/server/src/diagnostics/TraceDiagnostics.ts

@@ -90,8 +90,12 @@ function unixNanoToDateTime(value: unknown): DateTime.Utc | null {
   const text = toStringValue(value);
   if (!text) return null;
 
-  const millis = Number(BigInt(text) / 1_000_000n);
-  return Option.getOrNull(DateTime.make(millis));
+  try {
+    const millis = Number(BigInt(text) / 1_000_000n);
+    return Option.getOrNull(DateTime.make(millis));
+  } catch {
+    return null;
+  }
 }
 
 function readExitTag(exit: unknown): string | null {