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.

Plugin/unraid/System_Essentials/unraid_api_key_renew.sh

@@ -14,6 +14,29 @@
 # page always reflects the live key value.
 #
 # ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
+#
+# Self-Healing at Boot
+#   The unraid-api registry is ephemeral — OS updates and service restarts clear
+#   it without warning. Running at every array start means the key is always
+#   present after boot without any manual intervention.
+#
+# Conf Stays Current
+#   HOST*_UNRAID_API_KEY in the local host conf is updated after every renewal.
+#   The partnership page reads the conf — it always reflects the live key value
+#   without a separate sync step.
+#
+# ==============================================================================================
+# OPERATIONAL SAFEGUARDS
+# ==============================================================================================
+#
+#   acquire_lock    — prevents concurrent renewal attempts at boot
+#   detect_hosts()  — sets MY_ID to derive the correct conf var name
+#   Conf file check — aborts before any writes if the host conf is missing
+#   dry-run mode    — shows what would happen without touching anything
+#
+# ==============================================================================================
 # RUNTIME MODES
 # ==============================================================================================
 #