build, deploy, inbound, dmarc, backup, e2e: cite the source of what they rely on (assumptions part C)

Comments only, no behaviour changed. Each main.cf/master.cf parameter the
build sets, the wrapper's and the reload hook's reliance on Postfix 3.7.11
(postfix-script, master.5, postconf.5, cleanup_init.c, smtpd_peer.c,
README_FILES), supervisor 4.2.5 (process.py, options.py, events.rst),
logrotate 3.21.0, OpenDKIM's config, Cyrus SASL's sasldb, rspamd 3.11.1
(milter_headers.lua, multimap, the map watcher), Docker Compose, CoreDNS
and certbot now say where that is written. Measurements already there stay
measurements ("date not recorded" where none was); hand-composed fixtures
say so.

Contradictions left for their own commits: C-P31 cleanup's size limit,
C-P42 master outside supervisor's signal, C-V5/V6 startsecs, C-V10,
C-S3/Q3 sasldb written in place, C-Q4/A1 certbot's symlinks, C-R7 rspamd
skips local clients but the signature routine does not, C-P8, C-R4, C-R12,
C-M7, C-E2, C-K8/K9, C-D1.

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

build/logrotate-loop.sh

@@ -7,18 +7,35 @@
 # before the reload is lost. `create` (rather than `nocreate`) matters here
 # beyond timing: a postlogd-triggered recreate lands the file at 0600 owned by
 # postfix, which the unprivileged panel process cannot read — confirmed on a
-# live container — so logrotate must be the one to create it.
+# live container (date not recorded), and so in the source: Postfix 3.7.11,
+# src/util/logwriter.c, logwriter_open_or_die(), creates it 0644 under master's
+# umask(077), src/master/master.c — so logrotate must be the one to create it.
+# The reload: Postfix 3.7.11, conf/postfix-script, "logrotate" (mv, then kill
+# -HUP master); master_conf.c, master_config() -> master_restart_service() ->
+# master_status_cleanup(), on which postlogd exits (src/master/dgram_server.c,
+# dgram_server_abort() on MASTER_STATUS_FD), and the next postlogd opens the
+# path anew (src/postlogd/postlogd.c, logwriter_open_or_die()).
 #
 # logrotate itself only rotates once the configured "daily" period has elapsed
 # (tracked in /var/lib/logrotate/status), so it is safe to invoke this more
 # often than daily — polling merely bounds how late a legitimate rotation runs.
+# (logrotate 3.21.0-1: debian/rules, --with-state-file-path=/var/lib/logrotate/
+# status. That file is in the container's own filesystem: a recreated container
+# starts without it, and logrotate.c, newState(), records a log it has no state
+# for as rotated today, so the first rotation after a recreate comes a day
+# later.)
 set -eu
 
 CONFIG=/etc/logrotate.d/mail
 INTERVAL="${LOGROTATE_INTERVAL_SECONDS:-21600}"
 
 # logrotate refuses configs writable by group or others and exits 0 while
-# ignoring them — fail here so supervisord reports the fault.
+# ignoring them — fail here so supervisord reports the fault. (logrotate
+# 3.21.0, config.c, readConfigFile(): as root, mode & 0022 gives "Ignoring ...
+# because it is writable by group or others." and returns 0, not an error; a
+# config not owned by root is ignored the same way. "Potentially dangerous
+# mode" is only a warning there, for any mode & 07533 other than 0400 - this
+# loop chooses to treat it as fatal too.)
 logrotate_config_ok() {
 	mode=$(stat -c '%a' "$CONFIG")
 	mode=${mode#0}