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/emby_session_report.sh

@@ -18,6 +18,25 @@
 # configuration issue. Silent on clean runs.
 #
 # ==============================================================================================
+# DESIGN PRINCIPLES
+# ==============================================================================================
+#
+# No Persistent State
+#   Every report is generated fresh from the Emby API. No local database, no
+#   incremental tracking. A missed run leaves no gap — the next run simply
+#   covers its own window.
+#
+# Silent When Healthy
+#   The report goes to Discord/notification as a summary. Transcode alerts are
+#   the only proactive notification — high transcode ratios may indicate a
+#   misconfigured client that needs attention before it becomes a performance issue.
+#
+# Section Independence
+#   Each report section (sessions, library, activity, top content) guards its own
+#   API calls. A failure in one section does not abort the others — the report
+#   produces partial output rather than nothing.
+#
+# ==============================================================================================
 # OPERATIONAL SAFEGUARDS
 # ==============================================================================================
 #