fix(anim): remove frame swap — cursor now traverses all frames in reverse

ROOT CAUSE of "twitching" / stuck-on-frame-0 for reverse animations
(TurnRight with negative dat framerate, StrafeRight, etc.):

The frame swap (StartFrame↔EndFrame for negative speed) made EndFrame=0,
and GetStartFramePosition returned (0+1)-eps = 0.999. The cursor
oscillated between 0.0 and 0.999 — floor() of anything in [0,1) is
always 0, so only frame 0 ever rendered.

Fix: DON'T swap. Keep StartFrame=0, EndFrame=N-1 regardless of speed
sign. GetStartFramePosition for negative speed returns (N-1+1)-eps ≈ N,
so the cursor starts near the high end and counts down through ALL
frames. The Advance loop's reverse boundary check uses StartFrame (the
low value) correctly without the swap.

Also strips diagnostic logging from AnimationSequencer and GameWindow.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Tests/Physics/AnimationSequencerTests.cs

@@ -456,13 +456,12 @@ public sealed class AnimationSequencerTests
         // CurrentMotion should record the original TurnLeft command.
         Assert.Equal(TurnLeft, seq.CurrentMotion);
 
-        // After FUN_005267E0 (multiply_framerate) swaps low↔high for negative speed:
-        //   StartFrame = 3 (was high), EndFrame = 0 (was low)
-        // GetStartFramePosition for negative speed = (EndFrame + 1) - EPSILON = (0+1) - eps ≈ 0.99999.
-        // The cursor starts just below frame 1 and counts DOWN toward EndFrame(=0).
+        // Without swap: StartFrame=0, EndFrame=3 (original range preserved).
+        // GetStartFramePosition for negative speed = (EndFrame+1)-eps = (3+1)-eps ≈ 3.99999.
+        // The cursor starts near the HIGH end and counts DOWN toward StartFrame(=0).
         double pos = GetFramePosition(seq);
-        Assert.True(pos > 0.9 && pos < 1.0,
-            $"Expected framePosition near 0.99999 (reverse start near EndFrame+1) but got {pos}");
+        Assert.True(pos > 3.9 && pos < 4.0,
+            $"Expected framePosition near 3.99999 (reverse start near EndFrame+1) but got {pos}");
     }
 
     [Fact]