Allocate packet payloads with av_new_packet so they are freed through the
owning AVBufferRef instead of leaking on every decode. Pad extradata with
AV_INPUT_BUFFER_PADDING_SIZE for FFmpeg's bitstream parsers. Reject
oversized frames before the int cast, handle unexpected EOF in the
EAGAIN-retry loops, and add the missing <limits> include. Document the
valgrind codec check in docs/RUNBOOK.md.
Validated with valgrind: 0 bytes definitely lost, 0 invalid reads.
fegger
c6c062250e