feat: bundle yt-dlp and improve add modal usability

scripts/sync-ytdlp-bundle.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "$0")/.." && pwd)"
+DST_BASE="$ROOT_DIR/src-tauri/resources/engine"
+
+TMP_DIR="$(mktemp -d)"
+cleanup() {
+  rm -rf "$TMP_DIR"
+}
+trap cleanup EXIT
+
+mkdir -p "$DST_BASE/darwin/arm64" "$DST_BASE/darwin/x64"
+
+YTDLP_URL="${YTDLP_URL:-https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp_macos}"
+TARGET_FILE="$TMP_DIR/yt-dlp"
+
+echo "[sync-ytdlp] downloading: $YTDLP_URL"
+curl -fL "$YTDLP_URL" -o "$TARGET_FILE"
+chmod +x "$TARGET_FILE"
+
+cp "$TARGET_FILE" "$DST_BASE/darwin/arm64/yt-dlp"
+cp "$TARGET_FILE" "$DST_BASE/darwin/x64/yt-dlp"
+chmod +x "$DST_BASE/darwin/arm64/yt-dlp" "$DST_BASE/darwin/x64/yt-dlp"
+
+echo "[sync-ytdlp] copied to:"
+echo "  - $DST_BASE/darwin/arm64/yt-dlp"
+echo "  - $DST_BASE/darwin/x64/yt-dlp"