feat: animate queue sidebar expansion and collapse

README.md

@@ -67,7 +67,7 @@ The fixed bottom row holds the queue label/count and **+** on the left, with pre
 
 Queue rows show a medium-weight, two-line filename without its extension, with a smaller format label beneath it. Rows have a 56-point minimum height, 8-point vertical and 4-point horizontal internal padding, and no horizontal outer insets. The subdued remove button sits beneath the media icon in the left column, leaving the remaining width for the filename. The current item has an accent play marker and a subtle rounded highlight. Full filenames and paths remain available in row tooltips.
 
-In a normal window, showing the queue expands the window outward while preserving the video's size; hiding it removes that extra width. The sidebar meets the video directly, without a separate divider gap. The window shifts left when necessary near the screen's right edge. Fullscreen keeps its fixed bounds.
+The queue expands and collapses with a 250 ms ease-in/out reveal. In a normal window, the sidebar and window resize together while preserving the video's size; hiding it removes that extra width. Repeated toggles reverse from the current width without jumping. The sidebar meets the video directly, without a separate divider gap, and the window shifts left when necessary near the screen's right edge. Fullscreen animates the sidebar within its fixed bounds. Reduce Motion makes the change immediate; entering compact/fullscreen mode or starting a native resize settles an in-flight reveal first.
 
 Resizing with the queue open preserves the video's aspect ratio while keeping the sidebar at a fixed width; closing the queue retains ordinary aspect-locked video resizing.