test(playwright): token-endpoint tests tolerate DisableLogin

Under DisableLogin /auth/token deliberately answers 404 (lane K). The tests
now probe it: on a login-disabled rig TokenEndpoint_ReturnsJwt skips and the
bad-credentials test asserts 404 (the exchange is closed); with login enabled
they keep the 200 + JWT and 401 assertions.

tests/ZB.MOM.WW.ScadaBridge.CentralUI.PlaywrightTests/LoginTests.cs

@@ -74,15 +74,17 @@ public class LoginTests
         Assert.Equal(200, status); // redirect followed to login page
     }
 
-    /// <summary>Verifies that the token endpoint returns a JWT for valid credentials.</summary>
+    /// <summary>
+    /// Verifies that the token endpoint returns a JWT for valid credentials. Skipped when the
+    /// rig runs with <c>DisableLogin</c>, where <c>/auth/token</c> deliberately answers 404.
+    /// </summary>
     /// <returns>A task that represents the asynchronous operation.</returns>
-    [Fact]
+    [SkippableFact]
     public async Task TokenEndpoint_ReturnsJwt()
     {
-        var page = await _fixture.NewPageAsync();
-
-        await page.GotoAsync($"{PlaywrightFixture.BaseUrl}/login");
-        await page.WaitForLoadStateAsync(LoadState.DOMContentLoaded);
+        var page = await OpenLoginPageAsync();
+        Skip.If(await TokenEndpointDisabledAsync(page),
+            "Login is disabled on this rig: POST /auth/token answers 404 by design, so no JWT is issued.");
 
         var result = await page.EvaluateAsync<JsonElement>(@"
             async () => {
@@ -101,29 +103,50 @@ public class LoginTests
         Assert.Equal("multi-role", result.GetProperty("username").GetString());
     }
 
-    /// <summary>Verifies that the token endpoint returns HTTP 401 for invalid credentials.</summary>
+    /// <summary>
+    /// Verifies that the token endpoint rejects invalid credentials: HTTP 401 with login
+    /// enabled, or HTTP 404 under <c>DisableLogin</c> (the exchange is closed entirely, so
+    /// even bad credentials can never reach a credential check).
+    /// </summary>
     /// <returns>A task that represents the asynchronous operation.</returns>
     [Fact]
     public async Task TokenEndpoint_InvalidCredentials_Returns401()
     {
-        var page = await _fixture.NewPageAsync();
+        var page = await OpenLoginPageAsync();
+        var disabled = await TokenEndpointDisabledAsync(page);
 
+        var status = await PostTokenAsync(page, "baduser", "badpass");
+
+        Assert.Equal(disabled ? 404 : 401, status);
+    }
+
+    private async Task<IPage> OpenLoginPageAsync()
+    {
+        var page = await _fixture.NewPageAsync();
         await page.GotoAsync($"{PlaywrightFixture.BaseUrl}/login");
         await page.WaitForLoadStateAsync(LoadState.DOMContentLoaded);
+        return page;
+    }
 
-        var status = await page.EvaluateAsync<int>(@"
-            async () => {
+    /// <summary>
+    /// Probes whether the rig runs with <c>DisableLogin</c>: the token exchange then answers
+    /// 404 for any request (AuthEndpoints.HandleTokenAsync), while with login enabled a
+    /// valid-credential POST is a 200 and never a 404.
+    /// </summary>
+    private static async Task<bool> TokenEndpointDisabledAsync(IPage page) =>
+        await PostTokenAsync(page, PlaywrightFixture.TestUsername, PlaywrightFixture.TestPassword) == 404;
+
+    private static Task<int> PostTokenAsync(IPage page, string username, string password) =>
+        page.EvaluateAsync<int>(@"
+            async ([u, p]) => {
                 const resp = await fetch('/auth/token', {
                     method: 'POST',
                     headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
-                    body: 'username=baduser&password=badpass'
+                    body: new URLSearchParams({ username: u, password: p }).toString()
                 });
                 return resp.status;
             }
-        ");
-
-        Assert.Equal(401, status);
-    }
+        ", new object[] { username, password });
 
     private static ILocatorAssertions Expect(ILocator locator) =>
         Assertions.Expect(locator);