docs: stage 1 of the audit - log tailer, reconcile, sender check, guide

architecture.md
- § Log tailer: the rotation drain does not close the gap entirely
  (postlogd writes to the renamed file until the reload reaches it); the fix
  waits for the measurement. Delivery lines read at the head of the line
  (M12).
- § Queue reconcile: reason "reconcile", the 4 MiB cap, the conditional
  close; the measurement (delivery_log_days, its four counters) and the
  decision rule written before the data.
- § Sender check, what it costs: cleanup meets a check that hangs mid-message,
  with the warning seen on the stand; counted once per message.

guide.md
- § Outbound log: `bounced` is the panel's word when Postfix no longer holds
  a message and the log never said; it is counted.
- § Overview and Health, Sender check: the message a hung panel deferred is
  counted too.

Audit plan line ticked, roadmap 14/61. Stage 1's code items are done
(the two deferred tailer fixes wait for the data, as planned).

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

docs/audit-2026-10-12.md

@@ -636,7 +636,7 @@ has already run is never edited — the next file is added; the published
 - [x] **Deferred counter** (M13): on the stand, `kill -STOP` the panel mid-message
    and record which program logs the warning; widen the matcher accordingly
    and replace the composed fixture with the seen lines. — **Opus**
-- [ ] Docs: architecture § Log tailer, § Queue reconcile (the measurement and
+- [x] Docs: architecture § Log tailer, § Queue reconcile (the measurement and
    the rule), § Sender check "what it costs"; guide § Delivery log, § Health.
    — **Sonnet**