Frame-coupled VC-3/DNxHD MXF (_buildGrowingVc3Mxf) is now the only growing
master path. Delete provably-unreferenced legacy builders and their constants,
and update stale comments to match the VC-3 reality. No live-path behavior
change: the removed stop() raw2bmx branch was gated on a hard-coded false, so
the kept SIGINT path is byte-identical to the previously-executed else branch.
Removed (all confirmed unreferenced repo-wide outside this file):
- _buildGrowingOrchestrator() + JSDoc (raw2bmx bash orchestrator)
- _buildGrowingHevcMov() + JSDoc (HEVC fragmented-MOV growing)
- deriveGrowingRaster() (raw2bmx raster-flag mapper)
- growingVideoElementaryArgs() + GROWING_AVCI_CLASS
- GROWING_DEFAULT_BITRATE, GROWING_PART_INTERVAL_FRAMES,
GROWING_HEVC_DEFAULT_BITRATE, GROWING_VC3_CODECS (unused Set)
- isRaw2bmxGrowing dead branch in stop()
- stale raw2bmx/XDCAM HD422/AVC-Intra/frozen-picture comment blocks
Kept (live): _buildGrowingVc3Mxf, growingCodec, growingVc3Bitrate,
growingExtFor, GROWING_EXT, audioOffsetArgs (+AUDIO_OFFSET_MS), all
non-growing + network/SRT/RTMP/fc_pipe paths.
node --check passes.