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

scripts/setup-ytdlp.js

@@ -0,0 +1,89 @@
+#!/usr/bin/env node
+/**
+ * Downloads the standalone yt-dlp binary into ./bin so the app never depends on
+ * a system-wide install. The Linux/macOS builds are self-contained (no Python
+ * required). Run automatically on `npm install`, or manually with `npm run setup`.
+ */
+const fs = require('fs');
+const path = require('path');
+const https = require('https');
+
+const BIN_DIR = path.join(__dirname, '..', 'bin');
+const force = process.argv.includes('--force');
+
+function assetForPlatform() {
+  switch (process.platform) {
+    case 'win32':
+      return { asset: 'yt-dlp.exe', out: 'yt-dlp.exe' };
+    case 'darwin':
+      return { asset: 'yt-dlp_macos', out: 'yt-dlp' };
+    default:
+      // Linux (incl. WSL). yt-dlp_linux is a self-contained build.
+      return { asset: 'yt-dlp_linux', out: 'yt-dlp' };
+  }
+}
+
+function download(url, dest) {
+  return new Promise((resolve, reject) => {
+    const file = fs.createWriteStream(dest);
+    const get = (u, redirects = 0) => {
+      if (redirects > 10) return reject(new Error('Too many redirects'));
+      https
+        .get(u, { headers: { 'User-Agent': 'ytplayer-setup' } }, (res) => {
+          if (res.statusCode >= 300 && res.statusCode < 400 && res.headers.location) {
+            res.resume();
+            return get(res.headers.location, redirects + 1);
+          }
+          if (res.statusCode !== 200) {
+            res.resume();
+            return reject(new Error(`HTTP ${res.statusCode} for ${u}`));
+          }
+          const total = parseInt(res.headers['content-length'] || '0', 10);
+          let received = 0;
+          res.on('data', (chunk) => {
+            received += chunk.length;
+            if (total) {
+              const pct = ((received / total) * 100).toFixed(0);
+              process.stdout.write(`\r  downloading yt-dlp… ${pct}%`);
+            }
+          });
+          res.pipe(file);
+          file.on('finish', () => file.close(() => {
+            process.stdout.write('\r  downloading yt-dlp… done            \n');
+            resolve();
+          }));
+        })
+        .on('error', (err) => {
+          fs.unlink(dest, () => reject(err));
+        });
+    };
+    get(url);
+  });
+}
+
+async function main() {
+  const { asset, out } = assetForPlatform();
+  const dest = path.join(BIN_DIR, out);
+
+  if (!fs.existsSync(BIN_DIR)) fs.mkdirSync(BIN_DIR, { recursive: true });
+
+  if (fs.existsSync(dest) && !force) {
+    console.log(`yt-dlp already present at ${dest} (use "npm run update-ytdlp" to refresh).`);
+    return;
+  }
+
+  const url = `https://github.com/yt-dlp/yt-dlp/releases/latest/download/${asset}`;
+  console.log(`Fetching ${asset} from latest yt-dlp release…`);
+  try {
+    await download(url, dest);
+    if (process.platform !== 'win32') fs.chmodSync(dest, 0o755);
+    console.log(`yt-dlp installed at ${dest}`);
+  } catch (err) {
+    console.error('\nFailed to download yt-dlp automatically:', err.message);
+    console.error('You can place a yt-dlp binary manually in the ./bin folder, or ensure');
+    console.error('yt-dlp is on your PATH — the app will fall back to PATH if ./bin is empty.');
+    process.exitCode = 1;
+  }
+}
+
+main();