milter, postfix, app, domain: cite the source of what they rely on (assumptions part B)

Comments only, no behaviour changed. go-milter v0.4.1 (session.go: one
session per connection, replaced after a non-continue reply; macros per
stage), Postfix 3.7.11 (milter8.c, smtpd_check.c
reject_auth_sender_login_mismatch(), mail_addr_find.c, showq_compat.c,
mail_conf_time.c, mail_params.h), Cyrus SASL 2.1.28 (saslpasswd.c,
plugins/sasldb.c: deleting a missing login is not an error), OpenDKIM
2.11.0~beta2 (opendkim-db.c, opendkim-genkey), Berkeley DB 5.3 db_dump,
rspamd 3.11.0. Comments that claimed what the source denies are corrected
(sasldb keeps the password as given, not hashed; an embedded newline is
kept, not truncated; rspamd sorts symbols by absolute weight); fixtures say
seen or composed. The sender check's From: parsing gets no citations: it is
replaced by the port of OpenDKIM's dkim_mail_parse next.

Contradictions left for their own commits: B-G5 cleanAddress, B-PS1 first
key wins, B-PQ1 the forced-expire flag, B-PQ10/PQ11 Postfix's time units.

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

internal/postfix/queue.go

@@ -50,6 +50,11 @@ var postqueueP = func(ctx context.Context) *exec.Cmd {
 
 // listQueue runs `postqueue -p` and keeps at most maxQueueOutput bytes of it;
 // truncated says whether there was more.
+//
+// Postfix 3.7.11, src/postqueue/postqueue.c, show_queue(): any user passes
+// authorized_mailq_users (DEF_SHOWQ_ACL static:anyone), and a failure is
+// msg_fatal_status() - a non-zero exit with the reason on stderr;
+// src/postqueue/showq_compat.c, showq_compat(): "Mail queue is empty".
 func listQueue() (text string, truncated bool, err error) {
 	ctx, cancel := context.WithTimeout(context.Background(), postqueueTimeout)
 	defer cancel()
@@ -101,6 +106,9 @@ func Queue() (string, error) {
 // queue. A listing cut at the size cap is such an error: the messages past the
 // cut are still in the queue, and a backlog that large is the outage the sweep
 // exists for (audit 2026-10-12, H3). QueueMessages treats its cap the same way.
+//
+// Postfix 3.7.11, src/showq/showq.c, showq_service(): maildrop, active,
+// incoming, deferred and hold are the queues it lists.
 func QueueIDs() (map[string]struct{}, error) {
 	out, truncated, err := listQueue()
 	if err != nil {