[Feature] Add Minecraft in-game options editor

Emerald.CoreX/GameOptions/IMinecraftOptionsService.cs

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+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Emerald.CoreX.GameOptions;
+
+public interface IMinecraftOptionsService
+{
+    /// <summary>
+    /// Parses options.txt and loads the lang file from the version JAR.
+    /// Returns an empty list if options.txt does not exist yet.
+    /// </summary>
+    Task<MinecraftOptionsLoadResult> LoadAsync(
+        Game game,
+        CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Writes entries back to options.txt, preserving any keys that were
+    /// not parsed into MinecraftOptionEntry objects.
+    /// </summary>
+    Task SaveAsync(
+        Game game,
+        IEnumerable<MinecraftOptionEntry> entries,
+        CancellationToken cancellationToken = default);
+}
+
+public sealed class MinecraftOptionsLoadResult
+{
+    public IReadOnlyList<MinecraftOptionEntry> Entries { get; init; } = [];
+    public bool OptionsFileExists { get; init; }
+    /// <summary>Full original key→value map, used to round-trip unknown keys on save.</summary>
+    public IReadOnlyDictionary<string, string> OriginalRaw { get; init; }
+        = new Dictionary<string, string>();
+}

Emerald.CoreX/GameOptions/MinecraftOptionEntry.cs

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+using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using CommunityToolkit.Mvvm.ComponentModel;
+
+namespace Emerald.CoreX.GameOptions;
+
+public partial class MinecraftOptionEntry : ObservableObject
+{
+    public required string Key        { get; init; }
+    public required string DisplayName { get; init; }
+    public required MinecraftOptionType Type { get; init; }
+    public string   Category  { get; init; } = "General";
+    public double   SliderMin { get; init; }
+    public double   SliderMax { get; init; } = 1.0;
+    public double   SliderStep { get; init; } = 0.01;
+    public bool     SliderIsInt { get; init; }
+    public string?  SliderSuffix { get; init; }
+    public IReadOnlyList<MinecraftEnumOption> EnumOptions { get; init; } = [];
+
+    [ObservableProperty]
+    private string _rawValue = string.Empty;
+
+    partial void OnRawValueChanged(string value)
+    {
+        OnPropertyChanged(nameof(IsBooleanTrue));
+        OnPropertyChanged(nameof(SliderValue));
+        OnPropertyChanged(nameof(EnumRawValue));
+        OnPropertyChanged(nameof(SelectedEnumOption));
+        OnPropertyChanged(nameof(DisplayValueLabel));
+    }
+
+    // ── Boolean ──────────────────────────────────────────────────────────────
+    public bool IsBooleanTrue
+    {
+        get => RawValue == "true";
+        set => RawValue = value ? "true" : "false";
+    }
+
+    // ── Slider ───────────────────────────────────────────────────────────────
+    public double SliderValue
+    {
+        get => double.TryParse(RawValue, NumberStyles.Float,
+                   CultureInfo.InvariantCulture, out var d) ? d : SliderMin;
+        set
+        {
+            var rounded = SliderIsInt ? Math.Round(value) : value;
+            RawValue = SliderIsInt
+                ? ((int)rounded).ToString(CultureInfo.InvariantCulture)
+                : rounded.ToString(CultureInfo.InvariantCulture);
+            OnPropertyChanged();
+        }
+    }
+
+    // ── Enum ─────────────────────────────────────────────────────────────────
+    public string? EnumRawValue
+    {
+        get => RawValue.Trim('"');
+        set
+        {
+            RawValue = value is null ? string.Empty : $"\"{value}\"";
+            OnPropertyChanged();
+        }
+    }
+
+    public MinecraftEnumOption? SelectedEnumOption
+    {
+        get => EnumOptions.FirstOrDefault(o => o.RawValue == EnumRawValue);
+        set
+        {
+            if (value is not null) EnumRawValue = value.RawValue;
+            OnPropertyChanged();
+        }
+    }
+
+    // ── Display label ─────────────────────────────────────────────────────────
+    public string DisplayValueLabel => Type switch
+    {
+        MinecraftOptionType.Boolean     => IsBooleanTrue ? "On" : "Off",
+        MinecraftOptionType.SoundVolume => $"{(int)(SliderValue * 100)}%",
+        MinecraftOptionType.IntSlider   => SliderSuffix is null
+            ? $"{(int)SliderValue}"
+            : $"{(int)SliderValue}{SliderSuffix}",
+        MinecraftOptionType.FloatSlider => SliderSuffix is null
+            ? $"{SliderValue:F2}"
+            : $"{SliderValue:F1}{SliderSuffix}",
+        MinecraftOptionType.Enum => EnumOptions
+            .FirstOrDefault(o => o.RawValue == EnumRawValue)?.DisplayLabel
+            ?? EnumRawValue
+            ?? RawValue,
+        MinecraftOptionType.KeyBind => RawValue.TrimStart("key.".ToCharArray()),
+        _ => RawValue
+    };
+}
+
+public sealed record MinecraftEnumOption(string RawValue, string DisplayLabel);

Emerald.CoreX/GameOptions/MinecraftOptionType.cs

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+namespace Emerald.CoreX.GameOptions;
+
+public enum MinecraftOptionType
+{
+    Boolean,
+    IntSlider,
+    FloatSlider,
+    Enum,
+    KeyBind,
+    SoundVolume,
+    Skip
+}