Add a "wpt" dump mode

Adds a not-documented "wpt" mode to --dump which outputs a formatted
report.cases.

This is meant to make working on a single WPT test case easier, particularly
with some coding tool. Claude recommended this output for its own use.

Instead of telling claude to start the browser in serve mode, then run the
wptrunner, and merge the two outputs (and then stop the server), you can do:

zig build run -- fetch --dump wpt "http://localhost:8000/dom/nodes/CharacterData-appendChild.html"

(you still need the wpt server up)

src/Config.zig

@@ -185,6 +185,7 @@ pub const Serve = struct {
 pub const DumpFormat = enum {
     html,
     markdown,
+    wpt,
 };
 
 pub const Fetch = struct {

src/lightpanda.zig

@@ -105,11 +105,62 @@ pub fn fetch(app: *App, url: [:0]const u8, opts: FetchOpts) !void {
         switch (mode) {
             .html => try dump.root(page.window._document, opts.dump, writer, page),
             .markdown => try markdown.dump(page.window._document.asNode(), .{}, writer, page),
+            .wpt => try dumpWPT(page, writer),
         }
     }
     try writer.flush();
 }
 
+fn dumpWPT(page: *Page, writer: *std.Io.Writer) !void {
+    var ls: js.Local.Scope = undefined;
+    page.js.localScope(&ls);
+    defer ls.deinit();
+
+    var try_catch: js.TryCatch = undefined;
+    try_catch.init(&ls.local);
+    defer try_catch.deinit();
+
+    // return the detailed result.
+    const dump_script =
+        \\ JSON.stringify((() => {
+        \\   const statuses = ['Pass', 'Fail', 'Timeout', 'Not Run', 'Optional Feature Unsupported'];
+        \\   const parse = (raw) => {
+        \\     for (const status of statuses) {
+        \\       const idx = raw.indexOf('|' + status);
+        \\       if (idx !== -1) {
+        \\         const name = raw.slice(0, idx);
+        \\         const rest = raw.slice(idx + status.length + 1);
+        \\         const message = rest.length > 0 && rest[0] === '|' ? rest.slice(1) : null;
+        \\         return { name, status, message };
+        \\       }
+        \\     }
+        \\     return { name: raw, status: 'Unknown', message: null };
+        \\   };
+        \\   const cases = Object.values(report.cases).map(parse);
+        \\   return {
+        \\     url: window.location.href,
+        \\     status: report.status,
+        \\     message: report.message,
+        \\     summary: {
+        \\       total: cases.length,
+        \\       passed: cases.filter(c => c.status === 'Pass').length,
+        \\       failed: cases.filter(c => c.status === 'Fail').length,
+        \\       timeout: cases.filter(c => c.status === 'Timeout').length,
+        \\       notrun: cases.filter(c => c.status === 'Not Run').length,
+        \\       unsupported: cases.filter(c => c.status === 'Optional Feature Unsupported').length
+        \\     },
+        \\     cases
+        \\   };
+        \\ })(), null, 2)
+    ;
+    const value = ls.local.exec(dump_script, "dump_script") catch |err| {
+        const caught = try_catch.caughtOrError(page.call_arena, err);
+        return writer.print("Caught error trying to access WPT's report: {f}\n", .{caught});
+    };
+    try writer.writeAll("== WPT Results==\n");
+    try writer.writeAll(try value.toStringSliceWithAlloc(page.call_arena));
+}
+
 pub inline fn assert(ok: bool, comptime ctx: []const u8, args: anytype) void {
     if (!ok) {
         if (comptime IS_DEBUG) {