Add in-app browser with reader mode

Tapping a bookmark now opens an in-app WKWebView instead of bouncing to
Safari. Reader mode injects JS to extract article content and rerender
with clean serif typography and dark-mode support. Bottom toolbar has
back/forward, reader toggle, share, and open-in-Safari escape hatch.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Marks/Views/BrowserView.swift

@@ -0,0 +1,197 @@
+import SwiftUI
+import WebKit
+
+@Observable
+final class BrowserState: NSObject, WKNavigationDelegate {
+    let webView: WKWebView
+    var isLoading = false
+    var canGoBack = false
+    var canGoForward = false
+    var pageTitle = ""
+    var currentURL: URL?
+
+    init(url: URL) {
+        let config = WKWebViewConfiguration()
+        config.allowsInlineMediaPlayback = true
+        webView = WKWebView(frame: .zero, configuration: config)
+        super.init()
+        webView.navigationDelegate = self
+        webView.load(URLRequest(url: url))
+    }
+
+    func webView(_ webView: WKWebView, didStartProvisionalNavigation _: WKNavigation!) {
+        isLoading = true
+    }
+
+    func webView(_ webView: WKWebView, didCommit _: WKNavigation!) {
+        currentURL = webView.url
+        canGoBack = webView.canGoBack
+        canGoForward = webView.canGoForward
+    }
+
+    func webView(_ webView: WKWebView, didFinish _: WKNavigation!) {
+        isLoading = false
+        canGoBack = webView.canGoBack
+        canGoForward = webView.canGoForward
+        pageTitle = webView.title ?? ""
+        currentURL = webView.url
+    }
+
+    func webView(_: WKWebView, didFail _: WKNavigation!, withError _: Error) {
+        isLoading = false
+    }
+
+    func webView(_: WKWebView, didFailProvisionalNavigation _: WKNavigation!, withError _: Error) {
+        isLoading = false
+    }
+
+    func enterReaderMode(completion: @escaping () -> Void) {
+        webView.evaluateJavaScript(readerModeJS) { _, _ in
+            DispatchQueue.main.async { completion() }
+        }
+    }
+
+    func exitReaderMode() {
+        webView.reload()
+    }
+
+    private var readerModeJS: String {
+        """
+        (function() {
+            var title = document.title;
+            var selectors = ['article','[role="article"]','main','[role="main"]',
+                             '.post-content','.article-content','.entry-content',
+                             '.post-body','.article-body','.story-body','.content','#content'];
+            var content = null;
+            for (var i = 0; i < selectors.length; i++) {
+                var el = document.querySelector(selectors[i]);
+                if (el && (el.innerText||'').trim().length > 300) { content = el; break; }
+            }
+            if (!content) {
+                var best = { el: null, len: 0 };
+                Array.from(document.querySelectorAll('div')).forEach(function(d) {
+                    var len = Array.from(d.querySelectorAll('p')).reduce(function(a,p){return a+(p.innerText||'').length;},0);
+                    if (len > best.len) best = { el: d, len: len };
+                });
+                content = best.el || document.body;
+            }
+            var clone = content.cloneNode(true);
+            ['script','style','nav','header','footer','aside'].forEach(function(tag){
+                clone.querySelectorAll(tag).forEach(function(el){ el.remove(); });
+            });
+            var html = clone.innerHTML;
+            var css = [
+                'body{font-family:-apple-system,Georgia,serif;max-width:680px;margin:0 auto;',
+                'padding:20px 20px 60px;line-height:1.75;font-size:18px;background:#fafafa;color:#1c1c1e}',
+                'h1{font-size:1.6em;line-height:1.3;margin:0 0 .5em}',
+                'h2,h3,h4{line-height:1.35;margin:1.5em 0 .5em}p{margin:0 0 1em}',
+                'img{max-width:100%;height:auto;border-radius:8px;margin:8px 0}',
+                'a{color:#007aff;text-decoration:none}',
+                'blockquote{border-left:3px solid #ccc;margin:1em 0;padding:0 1em;color:#555}',
+                'code,pre{font-family:ui-monospace,monospace;font-size:.9em;background:#f0f0f0;border-radius:4px;padding:2px 4px}',
+                'pre code{padding:0;background:none}pre{padding:12px;overflow-x:auto}',
+                '@media(prefers-color-scheme:dark){body{background:#1c1c1e;color:#e5e5e7}',
+                'blockquote{border-color:#555;color:#aaa}code,pre{background:#2c2c2e}a{color:#0a84ff}}'
+            ].join('');
+            document.open();
+            document.write('<!DOCTYPE html><html><head>' +
+                '<meta name="viewport" content="width=device-width,initial-scale=1">' +
+                '<style>' + css + '</style>' +
+                '<title>' + title + '</title></head><body>' +
+                '<h1>' + title + '</h1>' + html + '</body></html>');
+            document.close();
+            return 'ok';
+        })()
+        """
+    }
+}
+
+private struct WebViewRepresentable: UIViewRepresentable {
+    let webView: WKWebView
+    func makeUIView(context: Context) -> WKWebView { webView }
+    func updateUIView(_ uiView: WKWebView, context: Context) {}
+}
+
+struct BrowserView: View {
+    let initialURL: URL
+    let initialTitle: String
+
+    @Environment(\.dismiss) private var dismiss
+    @Environment(\.openURL) private var openURL
+    @State private var state: BrowserState
+    @State private var readerMode = false
+
+    init(url: URL, title: String) {
+        self.initialURL = url
+        self.initialTitle = title
+        self._state = State(initialValue: BrowserState(url: url))
+    }
+
+    var body: some View {
+        NavigationStack {
+            ZStack(alignment: .top) {
+                WebViewRepresentable(webView: state.webView)
+                    .ignoresSafeArea(edges: .bottom)
+
+                if state.isLoading {
+                    ProgressView()
+                        .padding(.top, 8)
+                }
+            }
+            .navigationTitle(state.pageTitle.isEmpty ? initialTitle : state.pageTitle)
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .topBarLeading) {
+                    Button { dismiss() } label: {
+                        Image(systemName: "xmark")
+                            .fontWeight(.semibold)
+                    }
+                }
+                ToolbarItem(placement: .topBarTrailing) {
+                    Button {
+                        openURL(state.currentURL ?? initialURL)
+                    } label: {
+                        Image(systemName: "safari")
+                    }
+                }
+                ToolbarItemGroup(placement: .bottomBar) {
+                    Button {
+                        state.webView.goBack()
+                    } label: {
+                        Image(systemName: "chevron.left")
+                    }
+                    .disabled(!state.canGoBack)
+
+                    Spacer()
+
+                    Button {
+                        state.webView.goForward()
+                    } label: {
+                        Image(systemName: "chevron.right")
+                    }
+                    .disabled(!state.canGoForward)
+
+                    Spacer()
+
+                    Button {
+                        if readerMode {
+                            state.exitReaderMode()
+                            readerMode = false
+                        } else {
+                            state.enterReaderMode { readerMode = true }
+                        }
+                    } label: {
+                        Image(systemName: readerMode ? "doc.text.fill" : "doc.text")
+                    }
+                    .disabled(state.isLoading)
+
+                    Spacer()
+
+                    ShareLink(item: state.currentURL ?? initialURL) {
+                        Image(systemName: "square.and.arrow.up")
+                    }
+                }
+            }
+        }
+    }
+}