feat(pipeline): MP0 - wire FrameProfiler into GameWindow + DebugPanel toggle

GameWindow gets one field (_frameProfiler), one FrameBoundary() call at
the top of OnRender, three stage scopes (Update in OnUpdate, Upload
around _wbMeshAdapter?.Tick(), ImGui around _imguiBootstrap.Render()),
and one Dispose() call in teardown before _dats?.Dispose() releases the
GpuFrameTimer query ring. No new feature bodies land in GameWindow.cs —
all profiler logic lives in AcDream.App.Diagnostics.

DebugVM.FrameProf mirrors RenderingDiagnostics.FrameProfEnabled so the
DebugPanel checkbox ("Frame profiler ([frame-prof])") toggles the 5s
report live. Note: the checkbox lives in
AcDream.UI.Abstractions/Panels/Debug/DebugPanel.cs (IPanelRenderer,
backend-agnostic) alongside the other Diagnostics-section checkboxes —
not in AcDream.UI.ImGui, which holds no panel-drawing code per Code
Structure Rule 3.

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

src/AcDream.App/Rendering/GameWindow.cs

@@ -122,6 +122,11 @@ public sealed class GameWindow : IDisposable
     private readonly long[] _applyLockWaitSamples = new long[256];
     private int  _applyLockWaitSampleCursor;
 
+    // MP0 (2026-07-05): permanent frame profiler — one FrameBoundary call
+    // per OnRender + three stage scopes. All logic lives in
+    // AcDream.App.Diagnostics.FrameProfiler (structure rule 1).
+    private readonly AcDream.App.Diagnostics.FrameProfiler _frameProfiler = new();
+
     // Phase A.1: streaming fields replacing the one-shot _entities list.
     private AcDream.App.Streaming.LandblockStreamer? _streamer;
     private AcDream.App.Streaming.GpuWorldState _worldState = new();
@@ -7951,6 +7956,8 @@ public sealed class GameWindow : IDisposable
 
     private void OnUpdate(double dt)
     {
+        using var _updStage = _frameProfiler.BeginStage(AcDream.App.Diagnostics.FrameStage.Update);
+
         // [FRAME-DIAG]: applies run later this frame inside _streamingController.Tick;
         // flush the PREVIOUS OnUpdate's accumulated apply cost here (a clean per-frame
         // boundary, independent of where in OnUpdate the applies landed) and reset.
@@ -8755,6 +8762,8 @@ public sealed class GameWindow : IDisposable
 
     private void OnRender(double deltaSeconds)
     {
+        _frameProfiler.FrameBoundary(_gl!);
+
         // Phase G.1: set the clear color from the current sky's fog
         // tint so the horizon band continues naturally past the
         // rendered geometry. Fog blends to this color at max distance
@@ -8810,7 +8819,10 @@ public sealed class GameWindow : IDisposable
         // [FRAME-DIAG]: this OnRender drain is where staged GfxObj/entity meshes hit
         // the GPU (uncapped) — the H2 entity-upload suspect, separate from the apply.
         long fdE0 = _frameDiag ? System.Diagnostics.Stopwatch.GetTimestamp() : 0L;
+        using (var _uplStage = _frameProfiler.BeginStage(AcDream.App.Diagnostics.FrameStage.Upload))
+        {
             _wbMeshAdapter?.Tick();
+        }
         if (_frameDiag)
             FrameDiagPush(_entityUploadSamples, ref _entityUploadSampleCursor,
                 System.Diagnostics.Stopwatch.GetTimestamp() - fdE0);
@@ -9818,8 +9830,11 @@ public sealed class GameWindow : IDisposable
             // panels but still over the 3D scene. Cheap when no
             // selection — internal early-return on null guid.
             _targetIndicator?.Render();
+            using (var _imguiStage = _frameProfiler.BeginStage(AcDream.App.Diagnostics.FrameStage.ImGui))
+            {
                 _imguiBootstrap.Render();
             }
+        }
 
         // Update the window title with performance stats every ~0.5s.
         _perfAccum += deltaSeconds;
@@ -14005,6 +14020,7 @@ public sealed class GameWindow : IDisposable
         _uiHost?.Dispose();
         _textRenderer?.Dispose();
         _debugFont?.Dispose();
+        _frameProfiler.Dispose();   // MP0: releases the GpuFrameTimer query ring
         _dats?.Dispose();
         _input?.Dispose();
         _gl?.Dispose();

src/AcDream.UI.Abstractions/Panels/Debug/DebugPanel.cs

@@ -254,6 +254,12 @@ public sealed class DebugPanel : IPanel
         if (r.Checkbox("Probe auto-walk (ACDREAM_PROBE_AUTOWALK)",
                        ref probeAutoWalk))                              _vm.ProbeAutoWalk = probeAutoWalk;
 
+        // MP0 (2026-07-05): permanent frame profiler toggle — not a
+        // throwaway investigation probe, so it lives with the other
+        // always-available diagnostics rather than a dated section.
+        bool frameProf = _vm.FrameProf;
+        if (r.Checkbox("Frame profiler ([frame-prof])", ref frameProf)) _vm.FrameProf = frameProf;
+
         // ── Indoor rendering diagnostics (2026-05-19) ───────────────
         // Pinpoint where the EnvCell rendering chain breaks for
         // hypothesis-driven Phase 2 fix. Spec:

src/AcDream.UI.Abstractions/Panels/Debug/DebugVM.cs

@@ -291,6 +291,17 @@ public sealed class DebugVM
         set => PhysicsDiagnostics.ProbeAutoWalkEnabled = value;
     }
 
+    /// <summary>
+    /// Runtime mirror of <c>RenderingDiagnostics.FrameProfEnabled</c>
+    /// (env var <c>ACDREAM_FRAME_PROF</c>). Toggling here starts/stops the
+    /// [frame-prof] 5-second report live — no relaunch required.
+    /// </summary>
+    public bool FrameProf
+    {
+        get => RenderingDiagnostics.FrameProfEnabled;
+        set => RenderingDiagnostics.FrameProfEnabled = value;
+    }
+
     // ── Indoor rendering diagnostics (2026-05-19) ───────────────────
     // Mirror RenderingDiagnostics statics so DebugPanel checkbox toggles
     // take effect on the next render frame without relaunching.