Per CAIRO task brief 2026-09-26 [1] (D1-D6), Decision 6 mailbox
writes are ALWAYS AUTO_RUN against the sender's own home.
v4 did not implement this; v4.1 adds:
* MAILBOX_PATH_RE recognises <home-repo>/mailbox/(outbox|inbox)/<path>
for both coreci-<role>/home (standard) and coreci/<role>/home
(forward-compat).
* classify() extended with own-home gate: if every target is an
own-home mailbox path and no non-mailbox write verb is present,
classify AUTO_RUN.
* T18-T25 added; T8/T17 xfail preserved.
* deny_read_targets NOT implemented (per brief).
[1] CAIRO task brief - consolidated D1-D6
(per-home mailbox + read_targets parser)