FN-5698: clear OAuth relogin banner after successful login

Clear OAuth re-login banner entries immediately after provider re-authentication.

- add a shared oauth relogin success browser event constant in auth utilities
- dispatch relogin success events from Settings and Model Onboarding OAuth success flows
- update OAuthReloginBanner to listen for relogin success, optimistically clear matching provider rows, and trigger immediate status refresh
- add banner tests covering immediate clearing, refetch behavior, unrelated-provider events, and poll-only behavior
- document the immediate-clear behavior in dashboard docs and add a patch changeset for @runfusion/fusion

Files changed:
 .changeset/fn-5698-relogin-banner-auto-clear.md    |  5 ++
 docs/dashboard-guide.md                            |  4 +
 packages/dashboard/app/auth.ts                     |  1 +
 .../app/components/ModelOnboardingModal.tsx        |  3 +-
 .../app/components/OAuthReloginBanner.tsx          | 70 +++++++++--------
 .../dashboard/app/components/SettingsModal.tsx     |  3 +-
 .../__tests__/OAuthReloginBanner.test.tsx          | 90 ++++++++++++++++++++++
 7 files changed, 144 insertions(+), 32 deletions(-)

Fusion-Task-Id: FN-5698

Fusion-Task-Lineage: 1e2f8055-4f77-4e16-ac15-44891de13f55

packages/dashboard/app/components/SettingsModal.tsx

@@ -47,7 +47,7 @@ import { AgentProvisioningPolicyEditor } from "./AgentProvisioningPolicyEditor";
 import { SecretsView } from "./SecretsView";
 import { applyPresetToSelection, generateUniquePresetId } from "../utils/modelPresets";
 import { copyTextToClipboard } from "../utils/copyToClipboard";
-import { appendTokenQuery } from "../auth";
+import { appendTokenQuery, OAUTH_RELOGIN_SUCCESS_EVENT } from "../auth";
 import { useConfirm } from "../hooks/useConfirm";
 import { useMobileKeyboard } from "../hooks/useMobileKeyboard";
 import { useMobileScrollLock } from "../hooks/useMobileScrollLock";
@@ -1295,6 +1295,7 @@ export function SettingsModal({
             setAuthActionInProgress(null);
             clearAuthLoginUiState(providerId);
             addToast("Login successful", "success");
+            window.dispatchEvent(new CustomEvent(OAUTH_RELOGIN_SUCCESS_EVENT, { detail: { providerId } }));
             scrollSettingsToTop();
             return;
           }