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/system_tuning_monitor.sh

@@ -18,6 +18,24 @@
 # WebGUI slowdowns or timeouts under load.
 #
 # ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
+#
+# Snapshot for Trend, Not Just Alert
+#   Exhaustion events are rarely instant — they build over hours or days.
+#   Logging every 6 hours builds a trend that weekly_health_digest.sh can
+#   surface as a warning count, catching gradual pressure before it becomes
+#   an outage.
+#
+# Bounded Log Size
+#   Log entries are trimmed to TUNING_LOG_RETENTION days on every write.
+#   The log never grows unbounded regardless of how long the server runs.
+#
+# Silent When Healthy
+#   No output, no notification on a clean run. Threshold breach is the only
+#   signal — routine snapshots below the threshold produce nothing.
+#
+# ==============================================================================================
 # OPERATIONAL MODEL
 # ==============================================================================================
 #