Implement S256 challenge in OpenRouter OAuth flow (#5501)

* feat: implement S256 challenge in OpenRouter OAuth flow

* fix: add error handling for missing OpenRouter authorization code

* fix: save verifier to accountStorage

Co-authored-by: Copilot <copilot@github.com>

* fix: comment on getVerifierKey

---------

Co-authored-by: Copilot <copilot@github.com>

public/lib.js

@@ -24,6 +24,7 @@ import chalk from 'chalk';
 import yaml from 'yaml';
 import * as chevrotain from 'chevrotain';
 import { gzipSync, gzip } from 'fflate';
+import { sha256 } from 'js-sha256';
 
 /**
  * Expose the libraries to the 'window' object.
@@ -105,6 +106,7 @@ export default {
     chevrotain,
     gzipSync,
     gzip,
+    sha256,
 };
 
 export {
@@ -132,4 +134,5 @@ export {
     chevrotain,
     gzipSync,
     gzip,
+    sha256,
 };