Fix glTF pose sampled at the end of an animation returning a pose from the start (#6048)

GetPoseAtTimeGLTF searches for the interval containing the requested time
with (tstart <= time) && (time < tend). A time equal to the last keyframe
satisfies no interval, so the loop ends without a match and keyframe stays
at its 0 default, making the function return a pose from the beginning of
the animation.

LoadModelAnimationsGLTF samples at t = j/60 for j in [0, keyframeCount),
with keyframeCount = (int)(duration*60) + 1, so the last sample lands
exactly on the end of the animation whenever duration*60 is a whole
number. The last pose of those clips is wrong, which looks like a jerk
right before the animation ends.

Measured on a glTF with a 0.85 s clip: the delta between the last two
poses was 23x the median delta between consecutive poses; with this
change it is 0.3x, in line with every other step.

src/rmodels.c

@@ -6390,6 +6390,7 @@ static bool GetPoseAtTimeGLTF(cgltf_interpolation_type interpolationType, cgltf_
     float tstart = 0.0f;
     float tend = 0.0f;
     int keyframe = 0;       // Defaults to first pose
+    bool found = false;
 
     for (int i = 0; i < (int)input->count - 1; i++)
     {
@@ -6402,10 +6403,26 @@ static bool GetPoseAtTimeGLTF(cgltf_interpolation_type interpolationType, cgltf_
         if ((tstart <= time) && (time < tend))
         {
             keyframe = i;
+            found = true;
             break;
         }
     }
 
+    // No interval contains a time at (or past) the last keyframe, because the
+    // search above requires time < tend: clamp to the edge interval instead of
+    // falling back to keyframe 0, which returns a pose from the start
+    if (!found && ((int)input->count >= 2))
+    {
+        keyframe = (int)input->count - 2;
+
+        float tfirst = 0.0f;
+        if (!cgltf_accessor_read_float(input, 0, &tfirst, 1)) return false;
+        if (time < tfirst) keyframe = 0;
+
+        if (!cgltf_accessor_read_float(input, keyframe, &tstart, 1)) return false;
+        if (!cgltf_accessor_read_float(input, keyframe + 1, &tend, 1)) return false;
+    }
+
     // Constant animation, no need to interpolate
     if (FloatEquals(tend, tstart))
     {