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.

Tools/docker_prune_images.sh

@@ -20,6 +20,25 @@
 #   know all stopped containers are safe to delete.
 #
 # ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
+#
+# Safe Default, Explicit Escalation
+#   The default mode (dangling only) is always safe — running containers are
+#   never affected. The --all mode requires deliberate opt-in and carries an
+#   explicit caution in the description, because it removes stopped containers
+#   that may be intentionally paused.
+#
+# ==============================================================================================
+# OPERATIONAL SAFEGUARDS
+# ==============================================================================================
+#
+#   Root check   — Docker prune operations require root
+#   acquire_lock — prevents concurrent prune runs
+#   --dry-run    — shows what would be removed without taking any action
+#   --status     — lists current dangling images and stopped containers; no changes
+#
+# ==============================================================================================
 # RUNTIME MODES
 # ==============================================================================================
 #