fix #391: curated modern-only resolution list from the monitor's modes

User-directed (2026-08-13): "we should only support modern resolutions.
Not any old format." New DisplayModeCatalog enumerates the window's
monitor (Silk IMonitor.GetAllVideoModes) once at GameWindow load and
curates via a pure, tested rule: modern widescreen families only
(16:9/16:10/21:9/32:9 within 2.5%), at least 1280 wide, must fit the
desktop (an impossible windowed pick is not offered - the measured
3840x2160-on-2560x1440 silent clamp class), desktop mode always
included, refresh-rate duplicates collapsed, ascending order.

The Config Resolution row consumes the catalog through two new optional
Bind parameters; its Defaults value becomes the desktop's own mode.
Fixture/headless callers keep the static preset ladder, which now drops
800x600 and is pinned by test to pass the same curation rule (the OP6 S4
"default must be re-selectable" invariant holds on both paths).

Deliberate retail deviation, register row IA-22: retail listed the
adapter's complete enumeration including 4:3 legacy modes and authored
800x600 as the Config default (gmConfigUI::InitOptions
SetDefaultValue(0x03200258); gmClient::Init @0x004047af). The catalog is
also the designated fullscreen mode-switch validation source for
#376/#388 - an offered mode is supported by construction.

Tests: DisplayModeCatalogTests (8 - filter/clamp/dedupe/sort/ultrawide/
desktop-inclusion/fallback-consistency); ConfigOptionsPageControllerTests
row-12 default updated. App suite 4,961/3 skips; UI.Abstractions 916.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/AcDream.App.Tests/Rendering/DisplayModeCatalogTests.cs

@@ -0,0 +1,108 @@
+using AcDream.App.Rendering;
+using AcDream.UI.Abstractions.Panels.Settings;
+
+namespace AcDream.App.Tests.Rendering;
+
+/// <summary>#391 (user-directed): the curation rule that turns a monitor's
+/// raw mode enumeration into the modern-only resolution list. Pure-function
+/// tests — the Silk monitor adapter is a thin projection over this.</summary>
+public sealed class DisplayModeCatalogTests
+{
+    private static readonly (int W, int H) Desktop2560 = (2560, 1440);
+
+    [Fact]
+    public void Curate_DropsLegacyFormats_KeepsModernFamilies()
+    {
+        var modes = new (int, int)[]
+        {
+            (640, 480), (800, 600), (1024, 768), (1280, 1024),   // 4:3 / 5:4 legacy
+            (1280, 720), (1366, 768), (1600, 900), (1920, 1080), // 16:9
+            (1920, 1200),                                        // 16:10
+            (2560, 1440),
+        };
+
+        var curated = DisplayModeCatalog.Curate(modes, Desktop2560);
+
+        Assert.Equal(
+            ["1280x720", "1366x768", "1600x900", "1920x1080", "1920x1200", "2560x1440"],
+            curated);
+    }
+
+    [Fact]
+    public void Curate_ExcludesModesLargerThanTheDesktop()
+    {
+        // A windowed pick larger than the desktop can only silently clamp
+        // (measured live 2026-08-13: a 3840x2160 pick on this desktop
+        // produced a 2564x1421 window) — if it cannot exist, it is not
+        // offered.
+        var curated = DisplayModeCatalog.Curate(
+            [(1920, 1080), (2560, 1440), (3840, 2160)], Desktop2560);
+
+        Assert.Equal(["1920x1080", "2560x1440"], curated);
+    }
+
+    [Fact]
+    public void Curate_CollapsesRefreshRateDuplicates_AndSortsAscending()
+    {
+        // Real enumerations repeat each WxH once per refresh rate and are
+        // not ordered; the catalog is one entry per size, ascending.
+        var curated = DisplayModeCatalog.Curate(
+            [(2560, 1440), (1920, 1080), (1920, 1080), (1920, 1080), (1280, 720)],
+            Desktop2560);
+
+        Assert.Equal(["1280x720", "1920x1080", "2560x1440"], curated);
+    }
+
+    [Fact]
+    public void Curate_KeepsUltrawideFamilies()
+    {
+        var curated = DisplayModeCatalog.Curate(
+            [(2560, 1080), (3440, 1440), (3840, 1080)], (3840, 1600));
+
+        Assert.Equal(["2560x1080", "3440x1440", "3840x1080"], curated);
+    }
+
+    [Fact]
+    public void Curate_AlwaysIncludesTheDesktopModeItself()
+    {
+        // The desktop mode is displayable by definition — it stays even when
+        // its aspect matches no listed family (and it is the Defaults value).
+        var curated = DisplayModeCatalog.Curate(
+            [(1920, 1080), (1920, 1440)], (1920, 1440));   // desktop is 4:3!
+
+        Assert.Contains("1920x1440", curated);
+        Assert.Contains("1920x1080", curated);
+    }
+
+    [Fact]
+    public void Curate_DropsSubMinimumWidths_EvenWhenWidescreen()
+    {
+        // 1024x576 is exactly 16:9 but below the modern floor.
+        var curated = DisplayModeCatalog.Curate(
+            [(1024, 576), (1280, 720)], Desktop2560);
+
+        Assert.Equal(["1280x720"], curated);
+    }
+
+    [Fact]
+    public void FallbackPresetLadder_ItselfPassesTheCurationRule()
+    {
+        // The static fixture-fallback list must never offer something the
+        // production rule would reject (a big desktop accepts all of it).
+        var parsed = DisplaySettings.AvailableResolutions
+            .Select(static s => s.Split('x'))
+            .Select(static p => (int.Parse(p[0]), int.Parse(p[1])));
+
+        var curated = DisplayModeCatalog.Curate(parsed, (3840, 2160));
+
+        Assert.Equal(DisplaySettings.AvailableResolutions, curated);
+    }
+
+    [Fact]
+    public void FallbackDefault_IsAMemberOfTheFallbackList()
+    {
+        // The S4 rule survives the curation: the Defaults value must always
+        // be re-selectable from the offered list.
+        Assert.Contains(DisplaySettings.Default.Resolution, DisplaySettings.AvailableResolutions);
+    }
+}

tests/AcDream.App.Tests/UI/Layout/ConfigOptionsPageControllerTests.cs

@@ -726,7 +726,9 @@ public sealed class ConfigOptionsPageControllerTests
             90.0f,              // 10 Field Of View
             true,               // 11 Align To Slope
 
-            "800x600",          // 12 Resolution
+            "1280x720",         // 12 Resolution (#391: fixture fallback default —
+                                //    DisplaySettings.Default.Resolution; production
+                                //    passes the desktop mode via DisplayModeCatalog)
             true,               // 13 Full Screen
             false,              // 14 Sync To Refresh
             0f,                 // 15 Screen Brightness