feat(welcome): flavour loader + validation

windows/welcome/src/SilverOS.Welcome.Core/Flavours/FlavourLoader.cs

@@ -0,0 +1,25 @@
+using System.Text.Json;
+namespace SilverOS.Welcome.Core.Flavours;
+
+public sealed class FlavourValidationException(string message) : Exception(message);
+
+public sealed class FlavourLoader : IFlavourLoader
+{
+    public IReadOnlyList<FlavourManifest> Load(string directory)
+    {
+        var list = new List<FlavourManifest>();
+        foreach (var file in Directory.EnumerateFiles(directory, "*.json").OrderBy(f => f))
+        {
+            FlavourManifest m;
+            try { m = JsonSerializer.Deserialize<FlavourManifest>(File.ReadAllText(file), FlavourManifest.JsonOptions)
+                      ?? throw new FlavourValidationException($"{Path.GetFileName(file)}: empty"); }
+            catch (JsonException ex) { throw new FlavourValidationException($"{Path.GetFileName(file)}: {ex.Message}"); }
+            if (string.IsNullOrWhiteSpace(m.Id)) throw new FlavourValidationException($"{Path.GetFileName(file)}: missing id");
+            if (m.Hardening.Modules.Count == 0) throw new FlavourValidationException($"{Path.GetFileName(file)}: no hardening modules");
+            list.Add(m);
+        }
+        if (list.Count == 0) throw new FlavourValidationException("no flavour manifests found");
+        if (list.Count(m => m.IsDefault) != 1) throw new FlavourValidationException("exactly one flavour must be isDefault");
+        return list.OrderByDescending(m => m.IsDefault).ThenBy(m => m.Label).ToList();
+    }
+}

windows/welcome/src/SilverOS.Welcome.Core/Flavours/IFlavourLoader.cs

@@ -0,0 +1,2 @@
+namespace SilverOS.Welcome.Core.Flavours;
+public interface IFlavourLoader { IReadOnlyList<FlavourManifest> Load(string directory); }

windows/welcome/tests/SilverOS.Welcome.Tests/FlavourLoaderTests.cs

@@ -0,0 +1,38 @@
+using SilverOS.Welcome.Core.Flavours;
+using Xunit;
+
+public class FlavourLoaderTests
+{
+    private static string WriteTemp(params (string name, string json)[] files)
+    {
+        var dir = Directory.CreateTempSubdirectory("flav").FullName;
+        foreach (var (name, json) in files) File.WriteAllText(Path.Combine(dir, name), json);
+        return dir;
+    }
+
+    [Fact]
+    public void Loads_all_manifests_sorted_with_default_first()
+    {
+        var dir = WriteTemp(
+            ("privacy-max.json", """{ "id":"privacy-max","label":"Privacy-Max","hardening":{"modules":["00"]} }"""),
+            ("daily-driver.json", """{ "id":"daily-driver","label":"Daily-Driver","isDefault":true,"hardening":{"modules":["00"]} }"""));
+        var loaded = new FlavourLoader().Load(dir);
+        Assert.Equal(2, loaded.Count);
+        Assert.Equal("daily-driver", loaded[0].Id); // default first
+    }
+
+    [Fact]
+    public void Throws_when_a_manifest_has_no_id()
+    {
+        var dir = WriteTemp(("bad.json", """{ "label":"No Id","hardening":{"modules":["00"]} }"""));
+        var ex = Assert.Throws<FlavourValidationException>(() => new FlavourLoader().Load(dir));
+        Assert.Contains("bad.json", ex.Message);
+    }
+
+    [Fact]
+    public void Throws_when_no_default_flavour_present()
+    {
+        var dir = WriteTemp(("a.json", """{ "id":"a","label":"A","hardening":{"modules":["00"]} }"""));
+        Assert.Throws<FlavourValidationException>(() => new FlavourLoader().Load(dir));
+    }
+}