feat(centralui): Templates tree context menu — "New Instance…" (Deployer-gated)

Claude-Session: https://claude.ai/code/session_01G2GHPnbbKGvyyfbr2XBRVH

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/TemplatesPageTests.cs

@@ -47,15 +47,16 @@ public class TemplatesPageTests : BunitContext
         JSInterop.SetupVoid("treeviewStorage.save", _ => true);
     }
 
-    private void AddTestAuth()
+    private void AddTestAuth(params string[] roles)
     {
         // The page resolves the current user via the "Username" claim in
         // GetCurrentUserAsync(); supply a stub so OnInitializedAsync doesn't crash.
-        var claims = new[]
-        {
-            new Claim(JwtTokenService.UsernameClaimType, "tester"),
-            new Claim(JwtTokenService.RoleClaimType, "Designer")
-        };
+        // Calling this again from a test replaces the constructor's Designer-only
+        // default (MS DI resolves the LAST registration of a service), which is how
+        // a test renders the page as a Deployer.
+        if (roles.Length == 0) roles = new[] { Roles.Designer };
+        var claims = new List<Claim> { new(JwtTokenService.UsernameClaimType, "tester") };
+        claims.AddRange(roles.Select(r => new Claim(JwtTokenService.RoleClaimType, r)));
         var identity = new ClaimsIdentity(claims, "TestAuth");
         var user = new ClaimsPrincipal(identity);
         Services.AddSingleton<AuthenticationStateProvider>(new TestAuthStateProvider(user));
@@ -396,6 +397,57 @@ public class TemplatesPageTests : BunitContext
         Assert.EndsWith("/design/templates/create", nav.Uri);
     }
 
+    // ---------------------------------------------------------------
+    // "New Instance…" context-menu item (Deployer-gated)
+    // ---------------------------------------------------------------
+
+    private void SeedOneTemplate(int id, string name)
+    {
+        _repo.GetAllTemplatesAsync(Arg.Any<CancellationToken>())
+            .Returns(Task.FromResult<IReadOnlyList<Template>>(new List<Template> { new(name) { Id = id } }));
+        _repo.GetAllFoldersAsync(Arg.Any<CancellationToken>())
+            .Returns(Task.FromResult<IReadOnlyList<TemplateFolder>>(new List<TemplateFolder>()));
+    }
+
+    private static AngleSharp.Dom.IElement OpenTemplateContextMenu(
+        IRenderedComponent<TemplatesPage> cut, string label)
+    {
+        var row = cut.FindAll("li[role='treeitem']")
+            .First(li => li.TextContent.Contains(label))
+            .QuerySelector(".tv-row")!;
+        row.ContextMenu();
+        return cut.Find(".dropdown-menu.show");
+    }
+
+    [Fact]
+    public void TemplateContextMenu_OffersNewInstance_ForDeployer()
+    {
+        AddTestAuth(Roles.Designer, Roles.Deployer);
+        SeedOneTemplate(42, "Pump");
+
+        var cut = Render<TemplatesPage>();
+        var menu = OpenTemplateContextMenu(cut, "Pump");
+
+        var btn = menu.QuerySelector("button[data-test='ctx-new-instance']");
+        Assert.NotNull(btn);
+        Assert.Equal("New Instance…", btn!.TextContent.Trim());
+
+        btn.Click();
+        var nav = Services.GetRequiredService<NavigationManager>();
+        Assert.EndsWith("/deployment/instances/create?templateId=42", nav.Uri);
+    }
+
+    [Fact]
+    public void TemplateContextMenu_HidesNewInstance_ForDesignerOnly()
+    {
+        // The constructor already registered the Designer-only principal.
+        SeedOneTemplate(42, "Pump");
+
+        var cut = Render<TemplatesPage>();
+        var menu = OpenTemplateContextMenu(cut, "Pump");
+
+        Assert.Null(menu.QuerySelector("button[data-test='ctx-new-instance']"));
+    }
 }
 
 internal sealed class TestAuthStateProvider : AuthenticationStateProvider