fix(ext/sw): review fixes — storage key, timer reset scope, imports

- Rename storage key sessionTimeoutConfig → session_timeout (plan spec)
- Only call resetTimer() for non-content-script message types so content
  script polling cannot keep the session alive
- Collapse two same-module imports into one line; add CONTENT_CALLABLE_TYPES

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

extension/src/service-worker/router/popup-only.ts

@@ -361,7 +361,7 @@ export async function handle(
     case 'update_session_config': {
       sessionTimer.setConfig(msg.config);
       sessionTimer.resetTimer();
-      await chrome.storage.local.set({ sessionTimeoutConfig: msg.config });
+      await chrome.storage.local.set({ session_timeout: msg.config });
       return { ok: true };
     }
   }