Keep the macOS corner player layout from being squeezed

The separate player window could be resized below what the corner layout
needs. Free resize now floors at the corner layout's minimum (its width
threshold, the narrowest side column plus a video column wide enough for
the control bar, and 600pt tall), and an undersized window grows to it
when the corner layout takes over. The video column minimum is 560pt on
macOS so the control bar capsule fits.

The control bar's fixed 650pt frame also widened the controls stack past
a narrower video column, clipping the top bar's avatar and close button;
the frame is now capped to the container width.

Yattee/Views/Player/ExpandedPlayerWindowManager.swift

@@ -789,6 +789,7 @@ final class ExpandedPlayerWindowManager: NSObject {
             restoreOverlaySizingConstraints(on: window)
         } else {
             window.contentResizeIncrements = NSSize(width: 1, height: 1)
+            growToCornerLayoutMinimum(window)
         }
         LoggingService.shared.debug(
             "unlockAspectRatio (corner layout) aspect=\(window.contentAspectRatio) increments=\(window.contentResizeIncrements)",
@@ -796,6 +797,45 @@ final class ExpandedPlayerWindowManager: NSObject {
         )
     }
 
+    /// Smallest window the corner layout fits in: its width threshold (below
+    /// it the layout falls back to stacked), room for the narrowest side
+    /// column next to a video column wide enough for the controls, and
+    /// enough height for the video plus the below-video panel, capped to the
+    /// screen.
+    static func cornerLayoutMinimumSize(for screen: NSScreen?) -> NSSize {
+        let columnsWidth = CornerPlayerLayout<EmptyView>.minColumnWidth
+            + CornerPlayerLayout<EmptyView>.grabberWidth
+            + CornerPlayerLayout<EmptyView>.minVideoColumnWidth
+        var size = NSSize(
+            width: max(ExpandedPlayerSheet.minWidthForCornerLayout, columnsWidth),
+            height: ExpandedPlayerSheet.minHeightForCornerLayout
+        )
+        if let visibleFrame = screen?.visibleFrame {
+            size.width = min(size.width, visibleFrame.width)
+            size.height = min(size.height, visibleFrame.height)
+        }
+        return size
+    }
+
+    /// The corner layout resolves from window width only, so it can take over
+    /// a window shorter than it needs; grow the height (keeping the top edge)
+    /// so the floor `windowWillResize(_:to:)` enforces holds from the start.
+    private func growToCornerLayoutMinimum(_ window: NSWindow) {
+        guard !isActivePlayerWindowFullScreen else { return }
+        let screen = window.screen ?? NSScreen.main
+        let minimum = Self.cornerLayoutMinimumSize(for: screen)
+        var frame = window.frame
+        guard frame.width < minimum.width || frame.height < minimum.height else { return }
+        let top = frame.maxY
+        frame.size.width = max(frame.width, minimum.width)
+        frame.size.height = max(frame.height, minimum.height)
+        frame.origin.y = top - frame.height
+        if let screen {
+            frame = constrainToScreen(frame, screen: screen)
+        }
+        window.setFrame(frame, display: true, animate: true)
+    }
+
     // MARK: - Private Helpers
 
     private func synchronizeActiveWindowAspectRatio() {
@@ -1019,8 +1059,12 @@ extension ExpandedPlayerWindowManager: NSWindowDelegate {
                 // Free resize (corner layout): clamp each axis on its own.
                 // Preserving the proposal's ratio here would widen the window
                 // while the user drags only its bottom edge past the floor.
-                width = max(frameSize.width, 320)
-                height = max(frameSize.height, Self.minHeight)
+                // The floor is the corner layout's own minimum, so a drag
+                // can't squeeze the layout or push it under its width
+                // threshold (which would flip it to stacked mid-drag).
+                let minimum = Self.cornerLayoutMinimumSize(for: window.screen ?? NSScreen.main)
+                width = max(frameSize.width, minimum.width)
+                height = max(frameSize.height, minimum.height)
             }
 
             return NSSize(width: width, height: height)