Turn on strict memory safety for the macOS app

mac/Sources/Byre/MarkdownView.swift

@@ -112,7 +112,7 @@ struct InlineRenderer {
     private func run(_ s: String, _ style: Style) -> AttributedString {
         var a = AttributedString(s)
         a.font = Fonts.font(style.small ? 11 : size, weight: style.bold ? 700 : 400, italic: style.italic)
-        a.appKit.font = Fonts.ns(style.small ? 11 : size, weight: style.bold ? 700 : 400, italic: style.italic)
+        a.mergeAttributes(try! AttributeContainer([.font: Fonts.ns(style.small ? 11 : size, weight: style.bold ? 700 : 400, italic: style.italic)], including: \.appKit))
         if let link = style.link {
             a.link = link
         }
@@ -364,7 +364,7 @@ private struct FlowBuilder {
         s.append(NSAttributedString(string: "\n", attributes: [.font: Fonts.ns(ctx.size)]))
         let all = NSRange(location: 0, length: s.length)
         let color = NSColor(ctx.color)
-        s.enumerateAttribute(.foregroundColor, in: all) { value, range, _ in
+        unsafe s.enumerateAttribute(.foregroundColor, in: all) { value, range, _ in
             if value == nil {
                 s.addAttribute(.foregroundColor, value: color, range: range)
             }
@@ -405,8 +405,8 @@ private struct FlowText: NSViewRepresentable {
         v.isVerticallyResizable = false
         v.isHorizontallyResizable = false
         v.textContainerInset = .zero
-        v.textContainer!.lineFragmentPadding = 0
-        v.textContainer!.widthTracksTextView = true
+        unsafe v.textContainer!.lineFragmentPadding = 0
+        unsafe v.textContainer!.widthTracksTextView = true
         v.linkTextAttributes = [.cursor: NSCursor.pointingHand]
         v.delegate = context.coordinator
         return v
@@ -414,11 +414,11 @@ private struct FlowText: NSViewRepresentable {
 
     func updateNSView(_ v: FlowTextView, context: Context) {
         context.coordinator.openURL = context.environment.openURL
-        if v.textStorage!.isEqual(to: text) {
+        if unsafe v.textStorage!.isEqual(to: text) {
             return
         }
         let selected = v.selectedRanges
-        v.textStorage!.setAttributedString(text)
+        unsafe v.textStorage!.setAttributedString(text)
         if selected.allSatisfy({ NSMaxRange($0.rangeValue) <= text.length }) {
             v.selectedRanges = selected
         }