Update CSP to allow external fonts, scripts, and add corresponding test coverage

public/chat.html

@@ -439,7 +439,7 @@
         integrity="sha512-rCQgmUulW6f6QegOvTntKKb5IAoxTpGVCdWqYjkXEpzAns6XUFs8NKVqWe+KQpctp/EoRSFSuykVputqknLYMg=="
         crossorigin="anonymous" defer></script>
     <script src="/vendor/dompurify.js" defer></script>
-    <script type="module" src="/js/script.js?v=20260930-chat-usability"></script>
+    <script type="module" src="/js/script.js?v=20261007-chat-csp-fix"></script>
     <script type="module" src="/js/workspaceNavigation.js?v=20260909-account-controls"></script>
 </body>
 

public/js/script.js

@@ -1017,7 +1017,7 @@ if (headerModelButton) headerModelButton.addEventListener("click", (event) => {
 });
 saveGenerationSettingsBtn.addEventListener("click", () => { void saveGenerationSettings(); });
 roleplayNewPersonaBtn.addEventListener("click", closeRoleplayStarter);
-clearUserPersonaBtn.addEventListener("click", () => {
+if (clearUserPersonaBtn) clearUserPersonaBtn.addEventListener("click", () => {
     closeChatDrawer();
     void clearChatUserPersona();
 });