chore: onboarding/MFA-modal WIP, dev-workflow guidance, ideas updates

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/LoginGate.tsx

@@ -1,6 +1,7 @@
 import { useEffect, useState } from "react";
 import { api, BASE_URL, NetworkError } from "./api/client";
 import { showError } from "./banner";
+import { BannerStack } from "./components/BannerStack";
 import "./LoginGate.css";
 import App from "./App";
 import { OnboardingWizard } from "./OnboardingWizard";
@@ -58,17 +59,25 @@ export function LoginGate() {
   }, [status]);
 
   if (status === "loading") {
-    return <div className="login-gate-loading">Loading…</div>;
+    return (
+      <>
+        <BannerStack />
+        <div className="login-gate-loading">Loading…</div>
+      </>
+    );
   }
 
   if (status === "unauthenticated") {
     return (
-      <div className="login-gate">
-        <h1>🧞‍♀️ geniusrun</h1>
-        <a className="login-gate-button" href={`${BASE_URL}/api/session/login`}>
-          Log in
-        </a>
-      </div>
+      <>
+        <BannerStack />
+        <div className="login-gate">
+          <h1>🧞‍♀️ geniusrun</h1>
+          <a className="login-gate-button" href={`${BASE_URL}/api/session/login`}>
+            Log in
+          </a>
+        </div>
+      </>
     );
   }