Monitors echo/log audit pass

Status conclusions and clean-check summaries → echo: backup_verify (pre-flight
passed, all files match), bandwidth_monitor (logged transfer entry),
cert_monitor/smart_health (all healthy), system_tuning_monitor (snapshot written),
weekly_health_digest (smart no-findings exit, digest sent), zfs_memory_snapshot
(all pools ONLINE, all checks within thresholds). Manual-Monitors.md: added
Output Tiers section.

Monitors/Manual-Monitors.md

@@ -445,6 +445,21 @@ HOST2_ZFS_REPORT_IGNORE_POOLS=()
 
 ---
 
+## ━━━ OUTPUT TIERS ━━━
+
+All scripts use a two-tier output model: `echo` lines are always visible; `log`
+lines only appear when `--log` is passed.
+
+Most monitors are one-shot scripts that run on a schedule. Without `--log`, phase
+headers, step conclusions (pre-flight passed, snapshot written, digest sent), and
+the final status line are visible. Per-drive, per-cert, per-file, and per-domain
+detail lines inside loops are suppressed.
+
+`weekly_health_digest.sh` with `profile=smart` exits silently (one `echo` line)
+when there are no findings worth reporting — no noise on healthy weeks.
+
+---
+
 ## ━━━ FLAG REFERENCE ━━━
 
 All monitor scripts support the same four flags: