Fix compile errors: guard unwrap + ViewBuilder var mutation

- PRDetailView: guard let current = selectedTab ?? .overview fails because
  ?? already unwraps to non-optional. Use let current = selectedTab ?? .overview.
- MarkdownText: var inCodeBlock inside ViewBuilder is not allowed. Precompute
  lines with their code-block state as a computed property on a private struct,
  then iterate via ForEach in the builder. Bump to 3.3.

GiteaPR/Detail/PRDetailView.swift

@@ -195,8 +195,8 @@ struct PRDetailView: View {
             DragGesture(minimumDistance: 20)
                 .onEnded { value in
                     let tabs = DetailTab.allCases
-                    guard let current = selectedTab ?? .overview,
-                          let idx = tabs.firstIndex(of: current) else { return }
+                    let current = selectedTab ?? .overview
+                    guard let idx = tabs.firstIndex(of: current) else { return }
                     if value.translation.width < -40, idx < tabs.count - 1 {
                         withAnimation { selectedTab = tabs[idx + 1] }
                     } else if value.translation.width > 40, idx > 0 {

GiteaPR/Detail/Tabs.swift

@@ -179,49 +179,75 @@ struct MarkdownText: View {
         self.markdown = markdown
     }
 
+    /// One markdown source line with its render type resolved upfront, so the
+    /// code-block state doesn't have to be mutated inside the ViewBuilder.
+    private struct Line: Identifiable {
+        enum Kind { case code, heading, bullet, text, blank }
+        let id = UUID()
+        let kind: Kind
+        let text: String
+        let level: Int   // heading level
+    }
+
+    private var lines: [Line] {
+        let raw = markdown.components(separatedBy: "\n")
+        var out: [Line] = []
+        var inCodeBlock = false
+        for line in raw {
+            if line.hasPrefix("```") {
+                inCodeBlock.toggle()
+                continue
+            }
+            if inCodeBlock {
+                out.append(Line(kind: .code, text: line, level: 0))
+            } else if line.hasPrefix("# ") || line.hasPrefix("## ") || line.hasPrefix("### ") {
+                let level = line.prefix(while: { $0 == "#" }).count
+                out.append(Line(kind: .heading,
+                                text: String(line.dropFirst(level)).trimmingCharacters(in: .whitespaces),
+                                level: level))
+            } else if line.hasPrefix("- ") || line.hasPrefix("* ") {
+                out.append(Line(kind: .bullet,
+                                text: String(line.dropFirst(2)),
+                                level: 0))
+            } else if line.trimmingCharacters(in: .whitespaces).isEmpty {
+                out.append(Line(kind: .blank, text: "", level: 0))
+            } else {
+                out.append(Line(kind: .text, text: line, level: 0))
+            }
+        }
+        return out
+    }
+
     var body: some View {
         VStack(alignment: .leading, spacing: 6) {
-            let lines = markdown.components(separatedBy: "\n")
-            var inCodeBlock = false
-            ForEach(Array(lines.enumerated()), id: \.offset) { _, line in
-                if line.hasPrefix("```") {
-                    inCodeBlock.toggle()
-                } else if inCodeBlock {
-                    Text(line)
+            ForEach(lines) { line in
+                switch line.kind {
+                case .code:
+                    Text(line.text)
                         .font(.caption.monospaced())
                         .frame(maxWidth: .infinity, alignment: .leading)
                         .padding(4)
                         .background(Color(.secondarySystemBackground))
-                } else if line.hasPrefix("# ") || line.hasPrefix("## ") || line.hasPrefix("### ") {
-                    heading(line)
-                } else if line.hasPrefix("- ") || line.hasPrefix("* ") {
-                    bullet(line)
-                } else if line.trimmingCharacters(in: .whitespaces).isEmpty {
+                case .heading:
+                    Text(line.text)
+                        .font(line.level == 1 ? .title2.bold() : line.level == 2 ? .title3.bold() : .headline)
+                        .frame(maxWidth: .infinity, alignment: .leading)
+                case .bullet:
+                    HStack(alignment: .top, spacing: 6) {
+                        Text("•")
+                        inline(line.text)
+                    }
+                    .frame(maxWidth: .infinity, alignment: .leading)
+                case .blank:
                     Spacer(minLength: 4)
-                } else {
-                    inline(line)
+                case .text:
+                    inline(line.text)
                 }
             }
         }
         .frame(maxWidth: .infinity, alignment: .leading)
     }
 
-    private func heading(_ line: String) -> some View {
-        let level = line.prefix(while: { $0 == "#" }).count
-        let text = line.dropFirst(level).trimmingCharacters(in: .whitespaces)
-        return Text(text)
-            .font(level == 1 ? .title2.bold() : level == 2 ? .title3.bold() : .headline)
-            .frame(maxWidth: .infinity, alignment: .leading)
-    }
-
-    private func bullet(_ line: String) -> some View {
-        HStack(alignment: .top, spacing: 6) {
-            Text("•")
-            inline(String(line.dropFirst(2)))
-        }
-        .frame(maxWidth: .infinity, alignment: .leading)
-    }
-
     private func inline(_ text: String) -> some View {
         if let attributed = try? AttributedString(markdown: text) {
             Text(attributed)