Add ad-free YouTube player built on zero-native

Desktop YouTube player with no login and no ads. Extracts direct
video/audio streams with yt-dlp and plays them in a native window via
zero-native (Zig + system WebView) for a tiny footprint vs Electron.

- Dual-stream engine: muted video synced with separate audio track for
  high quality without ffmpeg muxing; progressive fallback
- On-device playlists, watch history, audio-only mode
- Full custom controls: seek, volume, speed, quality, fullscreen, queue
- Zig bridge handlers spawn yt-dlp and return slimmed JSON to the web UI
- Cinematic dark UI: Bricolage/Hanken/JetBrains Mono, vermilion accent

app.zon

@@ -0,0 +1,25 @@
+.{
+    .id = "com.ytplayer.app",
+    .name = "ytplayer",
+    .display_name = "YT Player",
+    .version = "1.0.0",
+    // System WebView (WKWebView / WebKitGTK) keeps the binary tiny vs. Electron.
+    .web_engine = "system",
+    .permissions = .{"window"},
+    .capabilities = .{ "webview", "js_bridge" },
+    .security = .{
+        .navigation = .{
+            // Local packaged UI + dev server. Media/images load from https at runtime.
+            .allowed_origins = .{ "zero://app", "http://127.0.0.1:5173" },
+        },
+    },
+    .windows = .{
+        .{ .label = "main", .title = "YT Player", .width = 1280, .height = 820 },
+    },
+    // Static web UI lives in ./frontend (no build step — plain HTML/CSS/JS).
+    .frontend = .{
+        .source = "packaged",
+        .dir = "frontend",
+        .entry = "index.html",
+    },
+}