Fallback echo/log audit pass — fallback.sh, fallback_test.sh + Manual

Remove setup banners from fallback.sh and fallback_test.sh. Add Host Detection
to fallback.sh OPERATIONAL SAFEGUARDS; add Lock Acquisition + Host Detection to
fallback_test.sh. Add output tiers section to Manual-Fallback.md documenting
daemon vs one-shot output behaviour.

Fallback/fallback_test.sh

@@ -60,6 +60,14 @@
 # Remote Docker Daemon Check
 #   Pre-flight confirms remote Docker daemon is responsive before Phase 2.
 #
+# Lock Acquisition
+#   acquire_lock() prevents concurrent test runs. Running two tests simultaneously
+#   would produce conflicting iptables rules and unreliable results.
+#
+# Host Detection
+#   detect_hosts() resolves MY_ID / REMOTE_ID from master.conf at startup.
+#   Exits if the host cannot be identified — prevents testing on an unknown machine.
+#
 # ==============================================================================================
 # CONFIGURATION
 # ==============================================================================================
@@ -134,8 +142,6 @@ trap cleanup EXIT
 # ==============================================================================================
 # ━━━ Setup ━━━
 # ==============================================================================================
-echo ""
-echo "━━━ $ICON_GEAR Setup ━━━"
 
 if [[ "$EUID" -ne 0 ]]; then
     error "Must be run as root"