Checkpoint: Append-Only Packet

In your editor: struct frame { unsigned char tag; unsigned short seq; unsigned int payload; };. Implement: 1. void frame_report(size_t *off_seq, size_t *off_payload, size_t *size) — offsetof/sizeof measured, not hardcoded. 2. Define struct frame_v2 { unsigned char tag; unsigned short seq; unsigned int payload; unsigned long long ts; }; and int frame_prefix_stable(void) — 1 iff tag/seq/payload offsets are identical between the versions (offsetof-verified). 3. unsigned long long sum_upto(int n, ...) — totals n unsigned ints passed variadic.