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.

System_Essentials/conf_cache_restore.sh

@@ -20,6 +20,30 @@
 #   RAM → backup removed → fallback.sh runs with last-known-good partner vars
 #
 # Own conf is never in the backup — it's always on disk.
+#
+# ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
+#
+# Remove After Use
+#   The persistent backup is always removed at the end of the run — whether it
+#   was used or not. Stale backups from a previous shutdown should never be left
+#   behind as a permanent fallback; the backup is a single-boot safety net, not
+#   a long-lived cache.
+#
+# Partner Only
+#   Own conf is on disk and is always available regardless of array or partner
+#   state. Only partner confs can be missing after a boot — only those are
+#   restored.
+#
+# ==============================================================================================
+# OPERATIONAL SAFEGUARDS
+# ==============================================================================================
+#
+#   require_partnership — exits early if PARTNERSHIP_ENABLED=false
+#   detect_hosts()      — determines which conf files belong to partners vs self
+#   No-backup guard     — exits cleanly if PERSISTENT_CONF_CACHE doesn't exist
+#
 # ==============================================================================================
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"