refactor(navigation): name the full-document loads the client router cannot serve

Nine places assigned window.location.href directly: OAuth connects and
sign-in hand-offs that land on API routes answering with a redirect, and
the reload after account deletion. The newer Next lint rule reads each as
an in-app page change. They now go through one helper that says why a
document load is the right tool there.

src/app/auth/login/page.tsx

@@ -25,6 +25,7 @@ import { isDashboardSnapshotEnabled } from "@/lib/dashboard/snapshot-flag";
 import { prefetchDashboardSnapshot } from "@/lib/queries/use-dashboard-snapshot";
 import { clearOfflineCachesForSessionEnd } from "@/lib/pwa/query-persister";
 import { sanitizeSameOriginPath } from "@/lib/url-safety";
+import { loadDocument } from "@/lib/navigation/load-document";
 
 export default function LoginPage() {
   const router = useRouter();
@@ -97,7 +98,7 @@ export default function LoginPage() {
 
   function handleOidcLogin() {
     const params = new URLSearchParams({ next: getRedirectTarget() });
-    window.location.href = `/api/auth/oidc/login?${params}`;
+    loadDocument(`/api/auth/oidc/login?${params}`);
   }
 
   function getRedirectTarget(): string {
@@ -126,7 +127,7 @@ export default function LoginPage() {
     // page always requires a fresh interactive login here (no ambient one-click
     // pass), which is exactly what the completion route's freshness rule needs.
     if (isNativeHandoff) {
-      window.location.href = "/api/auth/native/complete";
+      loadDocument("/api/auth/native/complete");
       return;
     }
     // Start the new session from an empty in-memory cache. The root

src/components/settings/advanced-section.tsx

@@ -21,6 +21,7 @@ import { SettingsCard } from "@/components/settings/settings-card";
 import { SettingsCardHeader } from "@/components/settings/_card-header";
 import { useTranslations } from "@/lib/i18n/context";
 import { apiFetchRaw } from "@/lib/api/api-fetch";
+import { loadDocument } from "@/lib/navigation/load-document";
 
 /**
  * Settings → Advanced.
@@ -225,7 +226,7 @@ function AccountDeleteCard() {
       // Leave `deleting` set so the confirm button keeps its pending
       // state through the redirect — the row is gone, nothing to undo.
       setTimeout(() => {
-        window.location.href = "/auth/login";
+        loadDocument("/auth/login");
       }, 1_500);
     } catch {
       setMsg(t("settings.deleteAccountFailed"));

src/components/settings/integrations/fitbit-card.tsx

@@ -70,6 +70,7 @@ import {
   IntegrationRedirectGuide,
 } from "./setup-guide-link";
 import type { IntegrationCallbackUrls } from "@/lib/integrations/callback-urls";
+import { loadDocument } from "@/lib/navigation/load-document";
 
 export function FitbitCard({
   viewModel,
@@ -511,7 +512,7 @@ export function FitbitCard({
               className="min-h-11 w-full sm:w-auto"
               data-testid="fitbit-connect"
               onClick={() => {
-                window.location.href = "/api/fitbit/connect";
+                loadDocument("/api/fitbit/connect");
               }}
             >
               <Link2 className="h-3.5 w-3.5" />

src/components/settings/integrations/google-health-card.tsx

@@ -85,6 +85,7 @@ import {
   IntegrationCardDescription,
 } from "./setup-guide-link";
 import type { IntegrationCallbackUrls } from "@/lib/integrations/callback-urls";
+import { loadDocument } from "@/lib/navigation/load-document";
 
 export function GoogleHealthCard({
   viewModel,
@@ -443,7 +444,7 @@ export function GoogleHealthCard({
               size="sm"
               variant="outline"
               onClick={() => {
-                window.location.href = "/api/google-health/connect";
+                loadDocument("/api/google-health/connect");
               }}
               data-testid="google-health-reconnect-button"
               className="min-h-11"
@@ -749,7 +750,7 @@ export function GoogleHealthCard({
               className="min-h-11 w-full sm:w-auto"
               data-testid="googlehealth-connect"
               onClick={() => {
-                window.location.href = "/api/google-health/connect";
+                loadDocument("/api/google-health/connect");
               }}
             >
               <Link2 className="h-3.5 w-3.5" />

src/components/settings/integrations/oauth-provider-card.tsx

@@ -72,6 +72,7 @@ import {
   type IntegrationDocsProvider,
 } from "./setup-guide-link";
 import type { IntegrationCallbackUrls } from "@/lib/integrations/callback-urls";
+import { loadDocument } from "@/lib/navigation/load-document";
 
 export interface OAuthProviderStatus {
   connected: boolean;
@@ -265,7 +266,7 @@ export function OAuthProviderCard({
   function handleConnect() {
     setMsg(null);
     void invalidateKeys(queryClient, measurementDependentKeys);
-    window.location.href = `/api/${provider}/connect`;
+    loadDocument(`/api/${provider}/connect`);
   }
 
   return (

src/components/settings/integrations/whoop-card.tsx

@@ -61,6 +61,7 @@ import {
   IntegrationRedirectGuide,
 } from "./setup-guide-link";
 import type { IntegrationCallbackUrls } from "@/lib/integrations/callback-urls";
+import { loadDocument } from "@/lib/navigation/load-document";
 
 export function WhoopCard({
   viewModel,
@@ -493,7 +494,7 @@ export function WhoopCard({
               className="min-h-11 w-full sm:w-auto"
               data-testid="whoop-connect"
               onClick={() => {
-                window.location.href = "/api/whoop/connect";
+                loadDocument("/api/whoop/connect");
               }}
             >
               <Link2 className="h-3.5 w-3.5" />

src/components/settings/integrations/withings-card.tsx

@@ -60,6 +60,7 @@ import {
   IntegrationRedirectGuide,
 } from "./setup-guide-link";
 import type { IntegrationCallbackUrls } from "@/lib/integrations/callback-urls";
+import { loadDocument } from "@/lib/navigation/load-document";
 
 export function WithingsCard({
   viewModel,
@@ -542,7 +543,7 @@ export function WithingsCard({
               className="min-h-11 w-full sm:w-auto"
               data-testid="withings-connect"
               onClick={() => {
-                window.location.href = "/api/withings/connect";
+                loadDocument("/api/withings/connect");
               }}
             >
               <Link2 className="h-3.5 w-3.5" />

src/lib/navigation/load-document.ts

@@ -0,0 +1,13 @@
+/**
+ * Leave the client router and load `path` as a new document.
+ *
+ * For destinations the client router cannot serve: an API route that answers
+ * with a redirect (an OAuth connect, a sign-in hand-off), or a page that has
+ * to start from a fresh document because the client state of the old one no
+ * longer belongs to anybody (after the account was deleted).
+ *
+ * In-app page changes use `useRouter().push()` instead.
+ */
+export function loadDocument(path: string): void {
+  window.location.assign(path);
+}