fix(qt): the player bar keeps the same 8 px gutter on macOS

The wider macOS gutter added for the Liquid Glass corner curve read as
excessive next to the 8 px the content pane keeps; one value on every
platform now, and the macOS-only theme token is gone with its comment.

cc

crates/qbz-qt/qml/theme/QbzTheme.qml

@@ -422,16 +422,10 @@ QtObject {
     /// The gutter the player bar keeps to the window's left, right and
     /// bottom edges (2026-09-13): the SAME 8 px the content pane keeps
     /// inside its frame, so the bar's ends line up with the pane's and
-    /// nothing in it touches the window edge.
+    /// nothing in it touches the window edge. One value on every platform:
+    /// a wider macOS gutter for the Liquid Glass corner was tried the same
+    /// day and read as too much.
     readonly property int npbGutter: 8
-    /// macOS only: Tahoe's Liquid Glass windows round their corners far
-    /// more than before (Apple: toolbar windows take a larger radius that
-    /// "can clip content that sits close to the edge of the window";
-    /// estimates run from ~12-16 pt for titlebar-only windows to 50 px+
-    /// with a toolbar) and the cover at the bar's left end lost its corner.
-    /// Qt has no LayoutRegion to nest content into the curve, so the bar
-    /// simply keeps a wider gutter there.
-    readonly property int npbGutterMac: 16
     // Every other bar mode (New / Classic / Large) — AppShell.slint:396.
     // The Large dock's sidebar reservation subtracts this, so it must be the
     // SAME value the shell pins the bar to.