feat(xai): prefilled OAuth device link, SuperGrok login label, trimmed model list (#6734)

- Use verification_uri_complete from the xAI device-code response so the
  login link opens with the user code prefilled (https-validated)
- Add OAuthAuth.loginLabel and show "Sign in with SuperGrok or X Premium"
  in the xAI auth-type selector (threaded through lazyOAuth)
- Remove grok-3, grok-3-fast, grok-4.20 variants and grok-code-fast-1
  from the built-in xAI catalog and default to grok-4.5

Co-authored-by: Jaaneek <Jaaneek@users.noreply.github.com>

packages/coding-agent/src/core/model-resolver.ts

@@ -26,7 +26,7 @@ export const defaultModelPerProvider: Record<KnownProvider, string> = {
 	"github-copilot": "gpt-5.4",
 	openrouter: "moonshotai/kimi-k2.6",
 	"vercel-ai-gateway": "zai/glm-5.1",
-	xai: "grok-4.20-0309-reasoning",
+	xai: "grok-4.5",
 	groq: "openai/gpt-oss-120b",
 	cerebras: "zai-glm-4.7",
 	zai: "glm-5.1",

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -4877,7 +4877,10 @@ export class InteractiveMode {
 	}
 
 	private showLoginAuthTypeSelector(providerOptions?: AuthSelectorProvider[]): void {
-		const subscriptionLabel = "Sign in with an account";
+		const oauthProvider = providerOptions?.find((provider) => provider.authType === "oauth");
+		const oauthLoginLabel =
+			oauthProvider?.method && "loginLabel" in oauthProvider.method ? oauthProvider.method.loginLabel : undefined;
+		const subscriptionLabel = oauthLoginLabel ?? "Sign in with an account";
 		const apiKeyLabel = "Sign in with an API key";
 		const availableAuthTypes = providerOptions
 			? new Set(providerOptions.map((provider) => provider.authType))