Close the last four headers, and say what the destructive tools refuse to do

Fallback/coverage_deploy.sh

@@ -42,7 +42,43 @@
 #       my-Foo.xml routinely holds a container called something else. Matching on the filename
 #       silently pushes the wrong template, or nothing at all.
 #
-# USAGE
+# OPERATIONAL SAFEGUARDS
+#   Only in NORMAL state. FALLBACK_STATE_FILE is read before anything is pushed or removed, and
+#   any other state refuses the action. A push during a live failover would deploy a second copy
+#   of a container the partner is currently running on our behalf; a remove would delete the one
+#   doing the covering.
+#
+#   --status is exempt from that gate, because it only reports. Refusing to answer "what is
+#   deployed over there" during a failover would withhold the information precisely when it is
+#   most wanted.
+#
+#   Every deploy is verified stopped, and a container that will not stay stopped is an error
+#   rather than a warning — see DESIGN PRINCIPLES. A second live instance against the same data
+#   is the failure this whole script exists inside.
+#
+#   Push and remove are explicit modes with no default. Running the script with no flag does
+#   nothing; neither action can be reached by accident, and neither is a side effect of editing
+#   the tier list.
+#
+#   --dry-run works in every mode and touches nothing on either host — no container is built,
+#   started, stopped or removed, and no template is written or deleted.
+#
+#   Remove deletes the container's appdata on the partner as well. That is deliberate and is the
+#   most destructive thing here; the NORMAL-state gate above is what keeps it away from a
+#   partner that is mid-handback.
+#
+# CONFIGURATION
+#   master.conf
+#     FALLBACK_<HOST>_TIER1..N   the covered container names — what --push deploys and --status
+#                                reports on. This script reads that list; it never edits it.
+#
+#   host*.conf
+#     FALLBACK_STATE_FILE        overrides where fallback.sh's state is read from. Defaults to
+#                                STATE_DIR/fallback_state.db. A missing file reads as NORMAL,
+#                                which is the correct default on a host where fallback has never
+#                                run.
+#
+# RUNTIME MODES
 #   coverage_deploy.sh --push            deploy every covered container onto the partner (stopped)
 #   coverage_deploy.sh --remove          stop, remove, and delete the pushed template on the partner
 #   coverage_deploy.sh --status          report, per covered container, whether it exists there