feat(linux): add graphical platform services

src/AcDream.UI.Abstractions/Input/KeyBindings.cs

@@ -18,7 +18,7 @@ namespace AcDream.UI.Abstractions.Input;
 /// K.1c: <see cref="RetailDefaults"/> now returns the full retail-faithful
 /// preset (byte-precise to <c>retail-default.keymap.txt</c>);
 /// <see cref="LoadOrDefault"/> + <see cref="SaveToFile"/> persist the
-/// table to JSON under <see cref="DefaultPath"/> with version-based
+/// table to JSON at a host-provided portable path with version-based
 /// migration. <see cref="AcdreamCurrentDefaults"/> is preserved as a
 /// reference for tests pinning the older WASD-only behavior, but is no
 /// longer the GameWindow startup source.
@@ -596,11 +596,4 @@ public sealed class KeyBindings
         return result;
     }
 
-    /// <summary>
-    /// Default path: <c>%LOCALAPPDATA%\acdream\keybinds.json</c>.
-    /// </summary>
-    public static string DefaultPath() => Path.Combine(
-        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
-        "acdream",
-        "keybinds.json");
 }

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

@@ -13,7 +13,8 @@ public readonly record struct UiWindowPosition(float X, float Y);
 /// <summary>
 /// JSON-backed persistence for non-keybind settings (Display today; future
 /// tabs Audio / Gameplay / Chat / Character will be added to the same
-/// file). Path: <c>%LOCALAPPDATA%\acdream\settings.json</c>. Coexists
+/// file). The graphical host supplies a canonical portable configuration
+/// path. Coexists
 /// with <c>keybinds.json</c>, which retains its own
 /// <see cref="Input.KeyBindings.LoadOrDefault"/> path.
 ///
@@ -41,12 +42,6 @@ public sealed class SettingsStore
         _path = path ?? throw new ArgumentNullException(nameof(path));
     }
 
-    /// <summary>Default path: <c>%LOCALAPPDATA%\acdream\settings.json</c>.</summary>
-    public static string DefaultPath() => Path.Combine(
-        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
-        "acdream",
-        "settings.json");
-
     /// <summary>
     /// Load Display settings. Missing file → <see cref="DisplaySettings.Default"/>.
     /// Missing individual keys fall back to the corresponding default