compileTimingAttrs/injectDurations used parseFloat, so data-start="intro"
wrote a NaN data-end and extract preferred that over duration; parseNumeric
now skips the id-ref (parseVideoElements already resolves it).
collectRenderMedia's resolveHostWindow likewise read host data-start with
parseFloat, so chained sub-composition slots (data-start="hook") stacked at
0-2s and every scene after the first rendered black. It now resolves host
starts through the shared resolveReferencedStart, matching the media parsers.
Fixes#3361.
Val
f52ec1c25f