Fix false array-start failure for start_webhook_listener.sh

No 'already running' guard existed — a relaunch (array stop/start that
doesn't kill the old node process) would exec straight into node, hit
EADDRINUSE on the port, and exit 1 within ~1s. array_started.sh correctly
reported that as a failure, even though the prior listener instance was
still healthy and serving webhooks the whole time. Confirmed live: the
node process from 2026-06-23 (PID 25977) is still running today, and the
2026-07-03 array start logged this exact false failure.

Added acquire_lock "continuous" before the exec — an existing, documented
common.sh mode (skip gracefully if a healthy instance is running) that
wasn't actually used anywhere in the codebase yet.

Arrs_Stack/start_webhook_listener.sh

@@ -27,8 +27,9 @@
 # ==============================================================================================
 #
 #   1. Check WEBHOOK_PORT — exit cleanly if 0 (listener disabled)
-#   2. Check WEBHOOK_SECRET — generate and persist one if empty
+#   2. acquire_lock "continuous" — exit cleanly if a healthy instance is already running
-#   3. exec node webhook_listener.js — replaces this process; PID stays the same
+#   3. Check WEBHOOK_SECRET — generate and persist one if empty
+#   4. exec node webhook_listener.js — replaces this process; PID stays the same
 #
 # exec is intentional: array_started.sh tracks the PID of this script to check
 # whether the listener is running. exec preserves that PID across the hand-off
@@ -53,11 +54,22 @@
 #   PID of this script to check liveness — exec ensures that PID continues to
 #   refer to the running node process after the hand-off.
 #
+# Continuous-Mode Lock, Not Just PID Tracking
+#   array_started.sh only checks whether ITS launch attempt is still alive after
+#   1s — it has no idea a previous instance might already be listening (e.g. an
+#   array stop/start that didn't kill the old node process). Without its own
+#   guard, a relaunch would exec straight into node, hit EADDRINUSE on the port,
+#   exit 1 almost immediately, and array_started.sh would log a false failure
+#   for a listener that was actually still healthy. acquire_lock "continuous"
+#   detects the live instance and exits 0 instead.
+#
 # ==============================================================================================
 # OPERATIONAL SAFEGUARDS
 # ==============================================================================================
 #
 #   WEBHOOK_PORT=0 gate  — exits cleanly before any setup if the listener is disabled
+#   acquire_lock "continuous" — exits 0 cleanly if a healthy instance is already running,
+#                          instead of relaunching into a port conflict
 #   Secret auto-generate — WEBHOOK_SECRET generated via openssl rand if empty;
 #                          persisted to master.conf immediately so restarts reuse it
 #   Shared secret gate   — webhook URL must include ?key=<WEBHOOK_SECRET>;
@@ -97,6 +109,11 @@ source "$ECOSYSTEM_ROOT/load_config.sh"
     exit 0
 }
 
+# Skip gracefully if a healthy instance is already listening — otherwise a
+# restart that doesn't kill the old node process (array stop/start without a
+# full reboot) hits EADDRINUSE and array_started.sh logs a false failure.
+acquire_lock "continuous"
+
 # ── Auto-generate secret if not yet set ─────────────────────────────────────
 if [[ -z "${WEBHOOK_SECRET:-}" ]]; then
     GENERATED=$(openssl rand -hex 32)