Replace macOS inline player sheet with full-window overlay

When "Play in a separate window" is disabled, the expanded player was a
native sheet attached to the main window. AppKit refuses fullscreen with
an attached sheet, so pressing F swapped the sheet for an in-window
overlay before fullscreening — a visible two-step transition.

Present the inline player as the full-window overlay from the start, so
fullscreen is just the window's native toggle. This removes the whole
sheet-swap machinery (toggleSheetFullScreen with its detach timing,
SheetWindowResizer, sheet sizing helpers).

- beginInlineOverlay/endInlineOverlay hide/restore the main window
  toolbar and mirror the window's fullscreen state into the renamed
  isMacInlinePlayerFullScreen flag via NSWindow notifications, so exits
  through Esc/green button/Mission Control stay in sync
- Collapsing exits fullscreen only if it was entered for the video
- Esc in the windowed overlay collapses to the mini bar via a new
  onCollapse callback (replacing the sheet's default Esc-dismiss)
- ContentView registers its hosting window (MainContentWindowReader) so
  the overlay targets the right window even when the setting is toggled
  while the Settings window has focus

Yattee/Views/Player/ExpandedPlayerSheet+Layouts.swift

@@ -1575,12 +1575,19 @@ extension ExpandedPlayerSheet {
                         // config first so a pinned window can enter fullscreen)
                         ExpandedPlayerWindowManager.shared.toggleFullScreen()
                     },
-                    // The coordinator flag covers overlay fullscreen (where the
+                    // The coordinator flag covers the inline overlay (where the
                     // main window is the fullscreen one) and, being @Observable,
                     // refreshes the button icon on toggle; the keyWindow check
                     // covers the separate-window presentation.
-                    isFullscreen: navigationCoordinator?.isMacPlayerFullScreenOverlay == true
+                    isFullscreen: navigationCoordinator?.isMacInlinePlayerFullScreen == true
                         || NSApp.keyWindow?.styleMask.contains(.fullScreen) == true,
+                    // Esc collapses the inline overlay to the mini bar; in
+                    // separate-window mode Esc keeps its default handling.
+                    onCollapse: appEnvironment?.settingsManager.macPlayerSeparateWindow == true
+                        ? nil
+                        : { [weak navigationCoordinator] in
+                            navigationCoordinator?.isPlayerExpanded = false
+                        },
                     onClose: { [self] in
                         closeVideo()
                     },