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

src/main.zig

@@ -0,0 +1,56 @@
+//! YT Player — zero-native app entry.
+//!
+//! This file shows how the App is wired to the runtime and how the bridge
+//! handlers in `bridge.zig` are registered. When you scaffold with
+//! `zero-native init`, a `src/main.zig` + `src/runner.zig` + `build.zig` are
+//! generated for your installed version. Merge the `bridge()` registration and
+//! the `handlers`/`policies` below into that generated App — the handler
+//! implementations themselves live in `bridge.zig` and need no changes.
+
+const std = @import("std");
+const zero_native = @import("zero_native");
+const handlers_impl = @import("bridge.zig");
+
+const Handler = zero_native.bridge.Handler;
+
+// Commands the UI is allowed to call, matched against window.zero.invoke names.
+const policies = [_]zero_native.bridge.CommandPolicy{
+    .{ .command = "yt.search" },
+    .{ .command = "yt.streams" },
+    .{ .command = "store.load" },
+    .{ .command = "store.save" },
+};
+
+pub const App = struct {
+    handlers: [4]Handler = undefined,
+
+    pub fn app(self: *App) zero_native.App {
+        return .{
+            .context = self,
+            .name = "YT Player",
+            // Serve the packaged static UI from the zero://app origin.
+            .source = zero_native.WebViewSource.packaged("frontend", "index.html"),
+            .bridge = bridge(self),
+        };
+    }
+
+    fn bridge(self: *App) zero_native.BridgeDispatcher {
+        self.handlers = .{
+            .{ .name = "yt.search", .context = self, .invoke_fn = handlers_impl.ytSearch },
+            .{ .name = "yt.streams", .context = self, .invoke_fn = handlers_impl.ytStreams },
+            .{ .name = "store.load", .context = self, .invoke_fn = handlers_impl.storeLoad },
+            .{ .name = "store.save", .context = self, .invoke_fn = handlers_impl.storeSave },
+        };
+        return .{
+            .policy = .{ .enabled = true, .commands = &policies },
+            .registry = .{ .handlers = &self.handlers },
+        };
+    }
+};
+
+pub fn main() !void {
+    var instance: App = .{};
+    var runtime = try zero_native.Runtime.init(std.heap.page_allocator);
+    defer runtime.deinit();
+    try runtime.run(instance.app());
+}