journal milter: recipients as Postfix logs them, once each

The row's recipient has to be the address Postfix writes in to=<..> or
orig_to=<..>, or the delivery line finds no row and the sweep closes it as
bounced. Postfix 3.7.11 hands the milter the RCPT argument as the client
wrote it (smtpd.c, milter_argv(); extract_addr() leaves it), go-milter
v0.4.1 trims "<>" and drops the ESMTP parameters (session.go, case
CodeRcpt) - so cleanAddress's cut at the first blank broke a quoted local
part (B-G5). Postfix keeps the address in internal form (tok822: quotes
off, backslash escapes taken) and logs it external
(info_log_addr_form.c, quote_822_local(): quoted again only when not a
dot-string); recipientAsLogged does the same, "ab"@x -> ab@x, "a b"@x
stays. A recipient given twice in any case is one row: cleanup drops the
duplicate, comparing folded (cleanup_out_recipient.c, been_here(),
BH_FLAG_FOLD; A-31). A rewritten recipient is matched by orig_to=, which
log_adhoc() writes only when it differs (A-9). The store's
case-insensitive match stays, now with its reason from the source (D-S20).

Stand (2026-10-14, make e2e, exit 0): new recipients_as_postfix_logs_them
- RCPT TO "x y"@, "ab"@ and "X Y"@ sink.e2e.test give two rows, "x
y"@sink.e2e.test and ab@sink.e2e.test, both sent. go vet and go test ./...
pass on the server; a unit test drives the milter through go-milter's own
client.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/store/sendlog.go

@@ -93,8 +93,15 @@ func (s *Store) InsertRejected(e SendLogEntry) error {
 
 // UpdateStatus advances the delivery status of the send-log rows matching a
 // (queue-id, recipient) pair, which the log-tailer parses out of mail.log.
-// Recipient matching is case-insensitive because Postfix may normalise address
-// case between the milter (envelope) and the delivery log. It returns the
+// Recipient matching is case-insensitive. Postfix keeps the case the client
+// wrote, and the milter's row holds it as Postfix logs it
+// (milter.recipientAsLogged); but a recipient repeated in another case is
+// one recipient to Postfix - cleanup drops the second, comparing folded
+// (Postfix 3.7.11, src/cleanup/cleanup_out_recipient.c, been_here() with
+// BH_FLAG_FOLD) - and one row to the milter, spelt as first given, and
+// log_adhoc() writes orig_to= only when it differs from to= other than in
+// case (src/global/log_adhoc.c, strcasecmp_utf8()). Assumptions D-S20. It
+// returns the
 // number of rows updated so the caller can tell whether the line matched a
 // journal entry.
 //