feat: replace normal fullscreen control with compact-mode button

README.md

@@ -22,7 +22,7 @@ The layout follows [IINA's video-first window](https://iina.io/img/screenshot.pn
 
 Opening video fits the window to its display aspect ratio, including non-square pixels, and constrains subsequent window resizing. Fullscreen retains the normal letterboxed renderer; audio-only playback and close release the aspect constraint. Extreme ratios that cannot fit both the screen and usable controls keep a freely resizable letterboxed window.
 
-**Compact mode** uses the same window, Metal view, and playback session—not a second window or macOS system PiP. Use **⌃⌘P** or **Playback Actions → Enter Compact Mode**. It starts at the current screen's bottom-right corner with a 16-point inset and a preferred width of 320 points, preserving display aspect where usable screen bounds and the 160 × 90-point minimum allow; extreme ratios retain letterboxing. Compact mode floats above ordinary windows, joins all Spaces, and is configured to join eligible other-app fullscreen spaces and Stage Manager sets. Small hover controls provide play/pause, restore, and Playback Actions; keyboard playback controls remain available.
+**Compact mode** uses the same window, Metal view, and playback session—not a second window or macOS system PiP. Use the PiP-shaped button in the normal playback controls, **⌃⌘P**, or **Playback Actions → Enter Compact Mode**. The compact-mode button replaces the fullscreen button; fullscreen remains available through its menu, keyboard shortcuts, and double-clicking normal-mode video. Compact mode starts at the current screen's bottom-right corner with a 16-point inset and a preferred width of 320 points, preserving display aspect where usable screen bounds and the 160 × 90-point minimum allow; extreme ratios retain letterboxing. Compact mode floats above ordinary windows, joins all Spaces, and is configured to join eligible other-app fullscreen spaces and Stage Manager sets. Small hover controls provide play/pause, restore, and Playback Actions; keyboard playback controls remain available.
 
 Drag the compact video to move the window; on release, each axis snaps independently when within 24 points of an inset usable-screen edge. **Snap to Screen Edges** is enabled by default and remembers its toggle across launches. Disabling snapping permits free placement. Exiting compact mode restores the previous normal geometry and window behavior, including keep-on-top; entry from fullscreen waits for the native exit animation, and restoring that session returns to fullscreen. Double-clicking compact video also restores the previous mode. Video replacement updates the compact aspect; audio-only replacement, playback errors, and closing the file leave compact mode. Closing the window still quits the app.
 

Sources/App/TerebiApp.swift

@@ -630,9 +630,8 @@ private struct PlayerContent: View {
                 }
                 Spacer(minLength: 8)
                 HStack(spacing: 12) {
-                    iconButton(model.isFullScreen ? "arrow.down.right.and.arrow.up.left" : "arrow.up.left.and.arrow.down.right",
+                    iconButton("pip.enter", "Enter Compact Mode", action: model.toggleCompact)
-                               model.isFullScreen ? "Exit Full Screen" : "Enter Full Screen", action: model.toggleFullScreen)
+                        .disabled(!model.canToggleCompact)
-                        .disabled(model.compactWindow.isTransitioning)
                     actionsMenu
                 }
                 .frame(width: 106, alignment: .trailing)