Old key was (page_key, chunk_len) which would incorrectly drop a second
config section that has the same length as the first (e.g. current-config
vs event-time-config when settings haven't changed).
New key is the full chunk bytes — only truly byte-identical chunks are
dropped. Different data that happens to share page_key and length now
comes through correctly.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>