feat(centralui): TemplatePathFormatter — folder-path label for template pickers

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

src/ZB.MOM.WW.ScadaBridge.CentralUI/Services/TemplatePathFormatter.cs

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+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates;
+
+namespace ZB.MOM.WW.ScadaBridge.CentralUI.Services;
+
+/// <summary>
+/// Renders a template's location as "Folder / Subfolder / Name" for the Create
+/// Instance template field and the picker footer. Pure; tolerates dangling or
+/// cyclic folder ids (stops after 32 hops) so a half-migrated catalogue never
+/// breaks the create page.
+/// </summary>
+public static class TemplatePathFormatter
+{
+    /// <summary>Separator placed between each folder segment and the template name.</summary>
+    public const string Separator = " / ";
+
+    /// <summary>
+    /// Builds the display path for <paramref name="template"/> by walking its
+    /// folder chain upward through <paramref name="foldersById"/>.
+    /// </summary>
+    public static string Format(Template template, IReadOnlyDictionary<int, TemplateFolder> foldersById)
+    {
+        var parts = new List<string> { template.Name };
+        var next = template.FolderId;
+        var hops = 0;
+        while (next is int id && foldersById.TryGetValue(id, out var folder) && hops++ < 32)
+        {
+            parts.Add(folder.Name);
+            next = folder.ParentFolderId;
+        }
+        parts.Reverse();
+        return string.Join(Separator, parts);
+    }
+}

tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/TemplatePathFormatterTests.cs

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+using ZB.MOM.WW.ScadaBridge.CentralUI.Services;
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates;
+
+namespace ZB.MOM.WW.ScadaBridge.CentralUI.Tests.Services;
+
+public class TemplatePathFormatterTests
+{
+    private static Dictionary<int, TemplateFolder> Folders(params TemplateFolder[] f) => f.ToDictionary(x => x.Id);
+
+    [Fact]
+    public void RootTemplate_IsNameOnly()
+    {
+        var t = new Template("Motor Controller") { Id = 1, FolderId = null };
+        Assert.Equal("Motor Controller", TemplatePathFormatter.Format(t, Folders()));
+    }
+
+    [Fact]
+    public void NestedTemplate_JoinsFolderChainWithSlashes()
+    {
+        var controllers = new TemplateFolder("Controllers") { Id = 10, ParentFolderId = null };
+        var conveyor = new TemplateFolder("Conveyor") { Id = 11, ParentFolderId = 10 };
+        var t = new Template("MES Line Controller") { Id = 1, FolderId = 11 };
+        Assert.Equal("Controllers / Conveyor / MES Line Controller",
+            TemplatePathFormatter.Format(t, Folders(controllers, conveyor)));
+    }
+
+    [Fact]
+    public void UnknownFolderId_FallsBackToNameOnly_WithoutThrowing()
+    {
+        var t = new Template("Orphan") { Id = 1, FolderId = 999 };
+        Assert.Equal("Orphan", TemplatePathFormatter.Format(t, Folders()));
+    }
+
+    [Fact]
+    public void FolderCycle_Terminates()
+    {
+        var a = new TemplateFolder("A") { Id = 1, ParentFolderId = 2 };
+        var b = new TemplateFolder("B") { Id = 2, ParentFolderId = 1 };
+        var t = new Template("T") { Id = 1, FolderId = 1 };
+        var s = TemplatePathFormatter.Format(t, Folders(a, b));
+        Assert.EndsWith("T", s); // no hang, no exception
+    }
+}