fix(demo): pace gait windows before buffering

Make the OpenGait-studio demo drop unpaced frames before they grow the silhouette window. Separate source-frame gap tracking from paced-frame stride tracking so runtime scheduling matches the documented demo-window-and-stride behavior.

Add regressions for paced window growth and schedule-frame stride semantics.

opengait-studio/opengait_studio/window.py

@@ -67,7 +67,8 @@ class SilhouetteWindow:
     stride: int
     gap_threshold: int
     _buffer: deque[Float[ndarray, "64 44"]]
-    _frame_indices: deque[int]
+    _source_frame_indices: deque[int]
+    _schedule_frame_indices: deque[int]
     _track_id: int | None
     _last_classified_frame: int
     _frame_count: int
@@ -91,12 +92,20 @@ class SilhouetteWindow:
 
         # Bounded storage via deque
         self._buffer = deque(maxlen=window_size)
-        self._frame_indices = deque(maxlen=window_size)
+        self._source_frame_indices = deque(maxlen=window_size)
+        self._schedule_frame_indices = deque(maxlen=window_size)
         self._track_id = None
         self._last_classified_frame = -1
         self._frame_count = 0
 
-    def push(self, sil: np.ndarray, frame_idx: int, track_id: int) -> None:
+    def push(
+        self,
+        sil: np.ndarray,
+        frame_idx: int,
+        track_id: int,
+        *,
+        schedule_frame_idx: int | None = None,
+    ) -> None:
         """Push a new silhouette into the window.
 
         Automatically resets buffer on track ID change or frame gap
@@ -112,8 +121,8 @@ class SilhouetteWindow:
             self.reset()
 
         # Check for frame gap
-        if self._frame_indices:
-            last_frame = self._frame_indices[-1]
+        if self._source_frame_indices:
+            last_frame = self._source_frame_indices[-1]
             gap = frame_idx - last_frame
             if gap > self.gap_threshold:
                 self.reset()
@@ -129,7 +138,10 @@ class SilhouetteWindow:
             )
 
         self._buffer.append(sil_array)
-        self._frame_indices.append(frame_idx)
+        self._source_frame_indices.append(frame_idx)
+        self._schedule_frame_indices.append(
+            frame_idx if schedule_frame_idx is None else schedule_frame_idx
+        )
         self._frame_count += 1
 
     def is_ready(self) -> bool:
@@ -152,7 +164,7 @@ class SilhouetteWindow:
         if self._last_classified_frame < 0:
             return True
 
-        current_frame = self._frame_indices[-1]
+        current_frame = self._schedule_frame_indices[-1]
         frames_since = current_frame - self._last_classified_frame
         return frames_since >= self.stride
 
@@ -185,15 +197,16 @@ class SilhouetteWindow:
     def reset(self) -> None:
         """Reset the window, clearing all buffers and counters."""
         self._buffer.clear()
-        self._frame_indices.clear()
+        self._source_frame_indices.clear()
+        self._schedule_frame_indices.clear()
         self._track_id = None
         self._last_classified_frame = -1
         self._frame_count = 0
 
     def mark_classified(self) -> None:
         """Mark current frame as classified, updating stride tracking."""
-        if self._frame_indices:
-            self._last_classified_frame = self._frame_indices[-1]
+        if self._schedule_frame_indices:
+            self._last_classified_frame = self._schedule_frame_indices[-1]
 
     @property
     def current_track_id(self) -> int | None:
@@ -212,9 +225,9 @@ class SilhouetteWindow:
 
     @property
     def window_start_frame(self) -> int:
-        if not self._frame_indices:
+        if not self._source_frame_indices:
             raise ValueError("Window is empty")
-        return int(self._frame_indices[0])
+        return int(self._source_frame_indices[0])
 
     @property
     def buffered_silhouettes(self) -> Float[ndarray, "n 64 44"]: