Use native text Close button for sheet toolbars on macOS

Sheet dismiss buttons rendered as an iOS-style circular glass "X" on
macOS 26, which looks foreign on the desktop. Add a shared
sheetCloseToolbarItem helper that renders a native text "Close" button
on macOS while keeping the compact icon-only xmark on iOS/tvOS, and
replace the ~14 duplicated inline close buttons across sheets with it.

Yattee/Extensions/ToolbarContent+Close.swift

@@ -0,0 +1,50 @@
+//
+//  ToolbarContent+Close.swift
+//  Yattee
+//
+//  Shared sheet-dismiss toolbar item.
+//
+
+import SwiftUI
+
+/// Standard sheet-dismiss toolbar item.
+///
+/// On macOS this renders a native text button (e.g. "Close"), which fits the desktop
+/// convention. On iOS/tvOS it renders the compact icon-only xmark used by the rest of
+/// the app's sheets.
+///
+/// Placement defaults to `.confirmationAction`; only the *label* changes per platform,
+/// so it can be dropped into existing `.toolbar { }` blocks without changing layout.
+@ToolbarContentBuilder
+func sheetCloseToolbarItem(
+    placement: ToolbarItemPlacement = .confirmationAction,
+    titleKey: LocalizedStringResource = "common.close",
+    identifier: String? = nil,
+    action: @escaping () -> Void
+) -> some ToolbarContent {
+    ToolbarItem(placement: placement) {
+        sheetCloseButton(titleKey: titleKey, identifier: identifier, action: action)
+    }
+}
+
+@ViewBuilder
+private func sheetCloseButton(
+    titleKey: LocalizedStringResource,
+    identifier: String?,
+    action: @escaping () -> Void
+) -> some View {
+    let button = Button(role: .cancel, action: action) {
+        #if os(macOS)
+        Text(String(localized: titleKey))
+        #else
+        Label(String(localized: titleKey), systemImage: "xmark")
+            .labelStyle(.iconOnly)
+        #endif
+    }
+
+    if let identifier {
+        button.accessibilityIdentifier(identifier)
+    } else {
+        button
+    }
+}