A reply to a case mail becomes a note on its record

Whatever reads the mailbox publishes on portal.mail.received; portal
appends the note after checking the record exists in a bucket this
site has and the sender is the address the record itself holds. A
note never moves a case: a mailbox is the one door anyone may knock
on, so it cannot drive a state machine even if someone forges their
way past the checks. The desks show the conversation beside the case.

Tested: the address parser, every refusal (a stranger, no address to
compare, an empty reply, the same reply twice, an unknown contract),
and the whole path through a real JetStream - the note lands, the
state does not move, and no event is written.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "portal"
-version = "0.3.47"
+version = "0.4.0"
 edition = "2021"
 
 [lib]