Fix low-FPS iOS PiP by reporting swaps while PiP is active

Since 1d9c5e3b performRender feeds swap timing to mpv via
mpv_render_context_report_swap, but only after presentRenderbuffer -
which is skipped while PiP is active. Once swap reports stop mid-stream,
display-vdrop's vsync estimation goes stale and mpv drops nearly every
frame (vo drop counter climbing ~19/s on a 24fps stream), turning PiP
into a slideshow.

The frame is genuinely displayed during PiP via the
AVSampleBufferDisplayLayer, so report the swap on that path too.

Yattee/Services/Player/MPV/MPVRenderView.swift

@@ -907,6 +907,12 @@ final class MPVRenderView: UIView {
                 // macOS render views already do this.
                 mpvClient.reportSwap()
             }
+        } else {
+            // PiP active: the frame is displayed via the PiP sample buffer layer instead
+            // of presentRenderbuffer. Keep feeding swap timing to mpv — display-vdrop
+            // relies on it once reports have started, and starving it makes mpv drop
+            // nearly every frame (low-FPS PiP).
+            mpvClient.reportSwap()
         }
 
         // Warn on GPU stalls: a render+present that takes far longer than a frame