Break the stage+commit window into sub-phases (FAT working-tree walk vs
object writes) via `commit split —` log lines, and add two micro-benchmarks
(sd_bench for SD/FAT primitive ops, git_bench for libgit2 object overhead)
with justfile recipes. Documents the walk-vs-writes cost model in
tradeoff-curves/sync-commit-staging.md to decide whether explicit-path
staging over the editor's dirty set is worth replacing add_all(["*"]).
New docs/notes/sync-latency.md breaks down the measured ~16 s cold :sync
(Wi-Fi + SNTP + one TLS push), explains the optimistic-retry handshake saving,
the reconcile/last-writer-wins semantics, and why the rest is near the protocol
floor. Linked from the notes index, the docs index, and the Git row of the root
README.
