feat(render): implement Campaign AR and terrain fidelity

src/AcDream.UI.Abstractions/Panels/Settings/DisplaySettings.cs

@@ -14,6 +14,117 @@ public enum ParticleRange
     Extended = 1,
 }
 
+/// <summary>
+/// Immutable, value-equal user overrides for one selected render pack. Keys
+/// are stable setting IDs and compare case-insensitively; values remain the
+/// declaration's invariant string representation until descriptor validation.
+/// </summary>
+public sealed class RenderPackSettingOverrides :
+    IReadOnlyDictionary<string, string>,
+    IEquatable<RenderPackSettingOverrides>
+{
+    private readonly SortedDictionary<string, string> _values;
+
+    public static RenderPackSettingOverrides Empty { get; } = new([]);
+
+    public RenderPackSettingOverrides(
+        IEnumerable<KeyValuePair<string, string>> values)
+    {
+        ArgumentNullException.ThrowIfNull(values);
+        _values = new SortedDictionary<string, string>(StringComparer.OrdinalIgnoreCase);
+        foreach ((string key, string value) in values)
+        {
+            ArgumentNullException.ThrowIfNull(key);
+            ArgumentNullException.ThrowIfNull(value);
+            _values[key] = value;
+        }
+    }
+
+    public int Count => _values.Count;
+
+    public IEnumerable<string> Keys => _values.Keys;
+
+    public IEnumerable<string> Values => _values.Values;
+
+    public string this[string key] => _values[key];
+
+    public bool ContainsKey(string key) => _values.ContainsKey(key);
+
+    public bool TryGetValue(string key, out string value) =>
+        _values.TryGetValue(key, out value!);
+
+    public IEnumerator<KeyValuePair<string, string>> GetEnumerator() =>
+        _values.GetEnumerator();
+
+    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() =>
+        GetEnumerator();
+
+    public RenderPackSettingOverrides Set(string settingId, string value)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(settingId);
+        ArgumentNullException.ThrowIfNull(value);
+        var next = new SortedDictionary<string, string>(
+            _values,
+            StringComparer.OrdinalIgnoreCase)
+        {
+            [settingId] = value,
+        };
+        return new RenderPackSettingOverrides(next);
+    }
+
+    public bool Equals(RenderPackSettingOverrides? other) =>
+        other is not null
+        && _values.Count == other._values.Count
+        && _values.All(pair => other._values.TryGetValue(pair.Key, out string? value)
+            && string.Equals(pair.Value, value, StringComparison.Ordinal));
+
+    public override bool Equals(object? obj) =>
+        obj is RenderPackSettingOverrides other && Equals(other);
+
+    public override int GetHashCode()
+    {
+        var hash = new HashCode();
+        foreach ((string key, string value) in _values)
+        {
+            hash.Add(key, StringComparer.OrdinalIgnoreCase);
+            hash.Add(value, StringComparer.Ordinal);
+        }
+        return hash.ToHashCode();
+    }
+}
+
+/// <summary>
+/// Stable, user-authored selection of one optional render pack. Logical ids
+/// are persisted instead of menu indexes so discovery order can never select a
+/// different pack or preset after an install/update. The renderer normalizes a
+/// missing, malformed, unavailable, or incompatible selection back to
+/// <see cref="Retail"/> and retains the precise reason for diagnostics.
+/// </summary>
+public sealed record RenderPackSelectionSettings(
+    string PackId,
+    string? PackVersion,
+    string PresetId)
+{
+    public const string RetailPackId = "retail";
+    public const string RetailPresetId = "off";
+
+    public static RenderPackSelectionSettings Retail { get; } = new(
+        RetailPackId,
+        PackVersion: null,
+        RetailPresetId);
+
+    /// <summary>
+    /// User-authored values keyed by the selected pack's stable setting IDs.
+    /// Empty by default so pre-render-pack settings files upgrade without a
+    /// migration write.
+    /// </summary>
+    public RenderPackSettingOverrides SettingOverrides { get; init; } =
+        RenderPackSettingOverrides.Empty;
+
+    public bool IsRetail =>
+        string.Equals(PackId, RetailPackId, StringComparison.OrdinalIgnoreCase);
+}
+
 /// <summary>
 /// Display-related preferences persisted to <c>settings.json</c>.
 /// Originally documented as "no retail equivalent for FOV / vsync etc" —
@@ -77,6 +188,16 @@ public sealed record DisplaySettings(
     bool BuildingDetailTextures = true,
     bool MultiPassAlpha = false)
 {
+    /// <summary>
+    /// Opt-in graphics enhancement selection. This is deliberately separate
+    /// from <see cref="Quality"/>, which remains the authoritative retail
+    /// renderer/streaming quality preset. Keeping the default here means an
+    /// upgraded settings file that predates shader packs deserializes to the
+    /// exact retail path without a migration write.
+    /// </summary>
+    public RenderPackSelectionSettings RenderPack { get; init; } =
+        RenderPackSelectionSettings.Retail;
+
     /// <summary>Values used on first launch / when settings.json is absent.
     /// Geometry defaults preserve the pre-L.0 runtime state: Resolution
     /// matches the WindowOptions startup size (1280×720). FieldOfView is