fix(ui): commit FramebufferResize + ResetPanelLayout — orphaned during earlier cwd/sed shenanigans

These changes were referenced by commits fc1e193 / 6273255 / 2818fcc /
df9f2fd in their messages but the actual edits sat uncommitted in the
working tree — caught by the pre-merge code review pass. Without this
commit the merge to main would lose all the panel-layout fixes the
user already live-verified.

What was orphaned:

 · _window.FramebufferResize += OnFramebufferResize  (Run() wiring)
 · OnFramebufferResize handler — updates GL viewport + camera aspect
   on window resize; force-resets panel layout via ResetPanelLayout.
 · ResetPanelLayout(ImGuiCond) — positions Vitals / Chat / Debug /
   Settings panels at sensible defaults relative to current window
   size. Called at startup with FirstUseEver (imgui.ini wins on later
   launches) and on FramebufferResize / View menu item with Always
   (force reset).
 · View → "Reset window layout" menu item.
 · OnLoad seeding ResetPanelLayout(FirstUseEver) after panel
   registration so first-launch users don't see all panels stacked
   at (0,0).
 · DisplaySettings.Default.Resolution: "1920x1080" → "1280x720" so
   the default matches the WindowOptions startup size — opening
   Display + Save without edits is a complete visual no-op (the
   alternative would have triggered an immediate resize on every
   first-time Save).

dotnet build green; tests unaffected.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -572,6 +572,12 @@ public sealed class GameWindow : IDisposable
         _window.Update += OnUpdate;
         _window.Render += OnRender;
         _window.Closing += OnClosing;
+        // L.0 Display tab: keep the GL viewport + camera aspect in sync
+        // with the window framebuffer. Without this handler, resizing
+        // the window (or applying a Display-tab Resolution change at
+        // startup) leaves the viewport pinned to the original size —
+        // user sees a small render in the corner of a big window.
+        _window.FramebufferResize += OnFramebufferResize;
 
         _window.Run();
     }
@@ -1058,6 +1064,14 @@ public sealed class GameWindow : IDisposable
                 }
 
                 Console.WriteLine("devtools: ImGui panel host ready (VitalsPanel + ChatPanel + DebugPanel + SettingsPanel registered)");
+
+                // L.0 Display tab: seed sensible default positions for
+                // every registered panel. cond=FirstUseEver means imgui.ini
+                // takes precedence on subsequent launches — the user's
+                // dragged positions persist. Without this, the first-run
+                // experience stacks every panel at (0,0) which looks
+                // broken.
+                ResetPanelLayout(ImGuiNET.ImGuiCond.FirstUseEver);
             }
             catch (Exception ex)
             {
@@ -4515,6 +4529,15 @@ public sealed class GameWindow : IDisposable
                     if (_debugPanel is not null
                         && ImGuiNET.ImGui.MenuItem("Debug", "Ctrl+F1"))
                         _debugPanel.IsVisible = !_debugPanel.IsVisible;
+                    ImGuiNET.ImGui.Separator();
+                    // L.0 Display tab: a manual reset for users whose
+                    // imgui.ini has saved a panel position that's now
+                    // off-screen (after a window shrink, monitor swap,
+                    // or a malformed save). Force-resets every panel
+                    // to its default landing position. The same code
+                    // path runs automatically on FramebufferResize.
+                    if (ImGuiNET.ImGui.MenuItem("Reset window layout"))
+                        ResetPanelLayout(ImGuiNET.ImGuiCond.Always);
                     ImGuiNET.ImGui.EndMenu();
                 }
                 // K-fix2 (2026-04-26): Camera submenu — discoverable
@@ -5408,6 +5431,78 @@ public sealed class GameWindow : IDisposable
     private AcDream.UI.Abstractions.Panels.Settings.SettingsStore? _settingsStore;
     private string _activeToonKey = "default";
 
+    /// <summary>
+    /// L.0 Display tab: framebuffer-resize handler — update GL viewport
+    /// + camera aspect when the window is resized (by the user dragging
+    /// the corner OR by ApplyDisplayWindowState applying a saved
+    /// Resolution). Without this, the viewport stays pinned at the
+    /// startup size, producing a small render inside a big window.
+    /// Also force-resets ImGui panel layout so panels that were
+    /// previously off the new viewport snap back to default positions.
+    /// </summary>
+    private void OnFramebufferResize(Silk.NET.Maths.Vector2D<int> newSize)
+    {
+        if (newSize.X <= 0 || newSize.Y <= 0) return;
+        _gl?.Viewport(0, 0, (uint)newSize.X, (uint)newSize.Y);
+        _cameraController?.SetAspect(newSize.X / (float)newSize.Y);
+        // Resize is always a force-reset — the alternative ("clamp
+        // existing positions") would require tracking each panel's
+        // current pos+size, which ImGuiNET doesn't expose by name.
+        // Force-reset is acceptable UX because resizing happens rarely
+        // and the user can always drag panels back where they want.
+        if (DevToolsEnabled && _imguiBootstrap is not null)
+            ResetPanelLayout(ImGuiNET.ImGuiCond.Always);
+    }
+
+    /// <summary>
+    /// L.0 Display tab: position every registered panel to its default
+    /// landing spot, computed relative to the current window size so
+    /// the layout adapts to any resolution. Called from:
+    /// <list type="bullet">
+    ///   <item>OnFramebufferResize (cond=Always — force-reset on resize).</item>
+    ///   <item>The View → "Reset window layout" menu item (cond=Always).</item>
+    ///   <item>OnLoad after panel registration (cond=FirstUseEver — only
+    ///         applies when imgui.ini has no saved position for that
+    ///         panel; on subsequent launches the saved positions win).</item>
+    /// </list>
+    /// </summary>
+    private void ResetPanelLayout(ImGuiNET.ImGuiCond cond)
+    {
+        if (_window is null) return;
+        float w = _window.Size.X;
+        float h = _window.Size.Y;
+        // Sane minimums so the math doesn't blow up on a tiny window.
+        if (w < 480) w = 480;
+        if (h < 320) h = 320;
+
+        // Panel positions chosen to be classic-MMO discoverable on a
+        // 1280x720 window: vitals top-left under the menu bar, chat
+        // bottom-left, debug top-right, settings centered. All sizes
+        // are reasonable defaults the user can resize from.
+        SetPanelLayout(_vitalsPanel?.Title,    new System.Numerics.Vector2(10f, 30f),
+                                                 new System.Numerics.Vector2(220f, 110f), cond);
+        SetPanelLayout(_chatPanel?.Title,      new System.Numerics.Vector2(10f, h - 320f),
+                                                 new System.Numerics.Vector2(450f, 300f), cond);
+        SetPanelLayout(_debugPanel?.Title,     new System.Numerics.Vector2(w - 380f, 30f),
+                                                 new System.Numerics.Vector2(370f, 520f), cond);
+        SetPanelLayout(_settingsPanel?.Title,  new System.Numerics.Vector2((w - 700f) * 0.5f, (h - 500f) * 0.5f),
+                                                 new System.Numerics.Vector2(700f, 500f), cond);
+    }
+
+    private static void SetPanelLayout(
+        string? title,
+        System.Numerics.Vector2 pos,
+        System.Numerics.Vector2 size,
+        ImGuiNET.ImGuiCond cond)
+    {
+        if (string.IsNullOrEmpty(title)) return;
+        // SetWindowPos/SetWindowSize by name work even when the window
+        // has never been Begin'd — ImGui stores the value for next
+        // appearance.
+        ImGuiNET.ImGui.SetWindowPos(title, pos, cond);
+        ImGuiNET.ImGui.SetWindowSize(title, size, cond);
+    }
+
     /// <summary>
     /// L.0 Display tab: apply the window-state-dependent settings
     /// (Resolution + Fullscreen) from a <see cref="AcDream.UI.Abstractions.Panels.Settings.DisplaySettings"/>

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

@@ -23,11 +23,14 @@ public sealed record DisplaySettings(
     bool ShowFps)
 {
     /// <summary>Values used on first launch / when settings.json is absent.
-    /// FieldOfView (60°) and VSync (false) match the camera + window
+    /// All defaults pinned to the pre-L.0 runtime state — Resolution
-    /// defaults that shipped before L.0, so opening Display + Save
+    /// matches the WindowOptions startup size (1280×720), FieldOfView
-    /// without touching anything is a visual no-op.</summary>
+    /// matches camera FovY (60°), VSync matches WindowOptions (false),
+    /// ShowFps preserves the perf string in the title bar. Net effect:
+    /// opening Display + Save without touching anything is a complete
+    /// visual no-op.</summary>
     public static DisplaySettings Default { get; } = new(
-        Resolution:   "1920x1080",
+        Resolution:   "1280x720",
         Fullscreen:   false,
         VSync:        false,
         FieldOfView:  60f,