feat(theme): ThemeScripts + localStorage nav-state enhancer

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/Components/ThemeScripts.razor

@@ -0,0 +1,4 @@
+@namespace ZB.MOM.WW.Theme
+@* Components/ThemeScripts.razor — drop before </body>. Emits the kit's nav-state
+   enhancer that persists NavRailSection open/closed state in localStorage. *@
+<script src="_content/ZB.MOM.WW.Theme/js/nav-state.js" defer></script>

ZB.MOM.WW.Theme/src/ZB.MOM.WW.Theme/wwwroot/js/nav-state.js

@@ -0,0 +1,22 @@
+// ZB.MOM.WW.Theme nav-state.js — persists <details data-nav-key> open/closed
+// state in localStorage so NavRailSection expand state survives navigation and
+// reloads. Pure client-side; works with static Blazor SSR. Keyed per section.
+(function () {
+    var PREFIX = "zbnav:";
+    function apply() {
+        document.querySelectorAll("details.rail-section[data-nav-key]").forEach(function (el) {
+            var key = PREFIX + el.getAttribute("data-nav-key");
+            var saved = null;
+            try { saved = window.localStorage.getItem(key); } catch (e) { return; }
+            if (saved === "1") el.open = true;
+            else if (saved === "0") el.open = false;
+            el.addEventListener("toggle", function () {
+                try { window.localStorage.setItem(key, el.open ? "1" : "0"); } catch (e) { /* ignore */ }
+            });
+        });
+    }
+    if (document.readyState === "loading")
+        document.addEventListener("DOMContentLoaded", apply);
+    else
+        apply();
+})();

ZB.MOM.WW.Theme/tests/ZB.MOM.WW.Theme.Tests/StaticAssetsTests.cs

@@ -35,6 +35,10 @@ public class StaticAssetsTests
     public void Fonts_are_vendored(string file) =>
         Assert.True(File.Exists(Path.Combine(Wwwroot, "fonts", file)));
 
+    [Fact]
+    public void NavStateScript_ships() =>
+        Assert.True(File.Exists(Path.Combine(Wwwroot, "js", "nav-state.js")));
+
     // Theme-002: .chip-idle pairs the idle background with the matching --idle
     // foreground token (per DESIGN-TOKENS.md), not --ink-soft.
     [Fact]

ZB.MOM.WW.Theme/tests/ZB.MOM.WW.Theme.Tests/ThemeScriptsTests.cs

@@ -0,0 +1,13 @@
+namespace ZB.MOM.WW.Theme.Tests;
+
+public class ThemeScriptsTests : TestContext
+{
+    [Fact]
+    public void ThemeScripts_emits_nav_state_script_tag()
+    {
+        var cut = RenderComponent<ThemeScripts>();
+        var script = cut.Find("script");
+        Assert.Equal("_content/ZB.MOM.WW.Theme/js/nav-state.js", script.GetAttribute("src"));
+        Assert.True(script.HasAttribute("defer"));
+    }
+}