nx_dash_get.nx

nx_dash_get.nx -- the DASH download ORCHESTRATOR (the parallel to nx_hls_get, composing this session's pieces): dash_parse (.mpd -> segment URLs) -> rdl_fetch_retry (per-segment retry + integrity, so a corrupt or dropped fragment is re-fetched, never stitched) -> concat (init + media) into one output. Format kind = RDL_GENERIC (DASH is fMP4/.m4s; the whole-fragment bar is non-empty; a fMP4-box check is a later rung). A live caller passes a TLS fetch_fn; the gate passes a failure-injecting one. Parallel = wrap pdl_download (nx_pardl, measured 4x) over the seglist -- a follow-on; this orchestrator is serial-with-retry.