14 pinning tests lock downloadAppUpdate's security invariants (redirect
re-validation per hop, checksum refusal paths, SHA-256 verify + cleanup,
truncation, idle-timeout, cancel in both phases, progress) with a
scripted net.request fake; then the nested streaming block is extracted
verbatim into streamInstallerToFile. downloadAppUpdate is now a linear
pre-flight; B6 cancel-slot ownership stays with its module state via
onCancelReady/onSettled. Pins green before and after.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
