Add full banner headers to all scripts across the codebase

Every script now has the established header format: PURPOSE with ─────── separator,
OPERATIONAL MODEL, DESIGN PRINCIPLES, OPERATIONAL SAFEGUARDS, CONFIGURATION, and
RUNTIME MODES — structured with full ====== banner sections throughout.

Orchestrators converted from compact ── inline format to full banners. Stale
emby-fallback and dirty sync references removed from Plugin/user_script_plug-in.sh.

Monitors/zfs_memory_snapshot.sh

@@ -15,6 +15,25 @@
 # comparison. In --dry-run mode, console only — nothing written to the log.
 #
 # ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
+#
+# Informational, Not Interventional
+#   This script reports — it does not act. system_watchdog.sh handles
+#   threshold-based intervention. Keeping the roles separate means the report
+#   is never suppressed by the same logic that triggers remediation.
+#
+# Week-Over-Week Comparison
+#   Output is written to ZFS_REPORT_LOG so the same snapshot can be reviewed
+#   across weeks. Memory pressure and ARC creep are slow — a single run is
+#   rarely conclusive; the trend across weeks is what matters.
+#
+# Section Independence
+#   Each of the five report sections guards its own data source. ZFS not
+#   available, Docker not responding — those sections skip, the rest still run.
+#   A partial report is more useful than no report.
+#
+# ==============================================================================================
 # OPERATIONAL MODEL
 # ==============================================================================================
 #