The registry response already carries each package file's size, so the
combined bar is sized from URLSource instead of a HEAD sweep; the probe,
its all-or-nothing fallback, and its duplicate Content-Length parsing are
gone, and archives without a reported size simply stay on the sequential
path. run_batch_downloads now takes (name, size, fetch) jobs and builds
the (now private) progress bar itself, collecting failures from future
results instead of a shared list; both call sites use functools.partial
instead of lambda factories. The prefetch touches only URLSource, so the
progress parameter comes off Source/Git/Local/ConvertedLibrary, and the
wave prefetch is wrapped best-effort like its ESP-IDF twin, which also
dedupes by dest only after the verifiability check. ProgressBar.done()
itself now skips the newline when no frame was drawn or the 100% frame
already ended the line, collapsing the batch wrapper's guard and fixing
the stray blank line after OTA uploads.