Give the application a settings area built from what really exists

tests/DodoSSH.Client.App.Layout.Tests/LayoutHarness.cs

@@ -55,6 +55,33 @@ internal static class LayoutHarness
     /// <remarks>v5b: 190 became 255, the design's own number rather than this bar's old approximation.</remarks>
     internal const double NavRailWidth = 255;
 
+    /// <summary>Settings mode's own rail, from <c>SettingsNav.axaml</c> — wider than <see cref="NavRailWidth"/>.</summary>
+    internal const double SettingsNavWidth = 340;
+
+    /// <summary>
+    /// The width settings mode's own content column asks for, from the design's <c>width:1100px</c>.
+    /// </summary>
+    /// <remarks>
+    /// A <c>MaxWidth</c> on the page, not a <c>Width</c> — see the same trade <c>TitleBar.axaml</c>'s own
+    /// search box makes with its own <c>MaxWidth="514"</c>, and for the identical reason:
+    /// <see cref="SettingsContentWidth"/> below is smaller than this at the window's minimum, and a page
+    /// that insisted on the full 1100 would arrange its own rows past the edge of the rectangle settings
+    /// mode actually gives them.
+    /// </remarks>
+    internal const double SettingsDesignContentWidth = 1100;
+
+    /// <summary>The width a settings page's content column actually gets at the window's minimum.</summary>
+    internal static double SettingsContentWidth => MinimumWidth - SettingsNavWidth;
+
+    /// <summary>What settings mode leaves a page between its own titlebar and the window's bottom edge.</summary>
+    /// <remarks>
+    /// Settings mode has no status bar and no update banner of its own — see <c>MainWindow.axaml</c>'s own
+    /// remark on why both are hidden while <c>IsSettingsMode</c> is true — so this is
+    /// <see cref="MinimumHeight"/> less only <see cref="TitleBarHeight"/>, not <see cref="ContentHeight"/>'s
+    /// own subtraction of <see cref="StatusBarHeight"/> too.
+    /// </remarks>
+    internal static double SettingsContentHeight => MinimumHeight - TitleBarHeight;
+
     /// <summary>
     /// What the titlebar and the status bar take off the window before any screen gets a pixel.
     /// </summary>
@@ -193,6 +220,18 @@ internal static class LayoutHarness
     /// <summary>The width a full-width screen gets, once the nav rail has taken its column.</summary>
     internal static double ScreenWidth => MinimumWidth - NavRailWidth;
 
+    /// <summary>
+    /// v5c-3: what the S3 usage of <c>TransfersScreen</c> gets, now that <c>MainWindow.axaml</c> gives it the
+    /// session shell's own 26px-padded, 1px-bordered LOOK with none of its machinery — no tab row, header,
+    /// status bar or sidebar to take further space off it.
+    /// </summary>
+    internal static double BucketsScreenWidth =>
+        ScreenWidth - (2 * SessionShellPadding) - (2 * SessionShellBorderThickness);
+
+    /// <inheritdoc cref="BucketsScreenWidth" />
+    internal static double BucketsScreenHeight =>
+        ScreenHeight - (2 * SessionShellPadding) - (2 * SessionShellBorderThickness);
+
     private static readonly HeadlessUnitTestSession Session =
         HeadlessUnitTestSession.GetOrStartForAssembly(typeof(LayoutHarness).Assembly);