chore(deploy): ship util-download in the production feature set

The deployed build only enabled `opentelemetry ai-openrouter`, so the
feature-gated `/util download` subcommand was compiled out in production.
Add `util-download` so redeploys include it. The host must have `yt-dlp`
and `ffmpeg` (with `ffprobe`) on PATH at runtime.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: 1Git2Clone

scripts/deploy-features.sh

@@ -3,4 +3,4 @@
 # bg-deploy.sh sources this for its default; the CI build/clippy matrix
 # mirrors the same string with a comment pointing here.
 # shellcheck disable=SC2034
-DEPLOY_FEATURES="opentelemetry ai-openrouter"
+DEPLOY_FEATURES="opentelemetry ai-openrouter util-download"