The private-media preflight applied Android's 256-fragment reassembly
cap to every directed media send, including the encrypted 0x20 path.
That regressed iOS→iOS private photos in the ~120-512 KiB range, which
work today: iOS reassembles up to 10,000 fragments and main compresses
images to <=512 KiB.
Encrypted private media is only ever sent to peers that advertised the
.privateMedia capability (modern clients with the full receiver
ceiling); current Android receives private media exclusively over the
directed raw-file migration fallback. Restrict the 256-fragment cap to
that fileTransfer fallback path so capable peers use the normal ceiling.
Leaves a TODO(#1434) to negotiate an explicit per-peer fragment limit
for a future Android client that adopts 0x20 but keeps a small
reassembler.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
