Add runbook for recovering wedged units and new scripts for device management

- Created a comprehensive runbook (`wedged_unit_recovery.md`) detailing the recovery process for units stuck in a call-home loop, including symptoms, recovery steps, and explanations of the failure mode.
- Added `blind_stop.sh` script to send stop-monitoring commands in a tight loop for unresponsive devices.
- Introduced `rescue_device.sh` script to disable Auto Call Home and erase events from a busy device.
- Implemented `slow_drip.sh` script to send stop-monitoring frames at a slow rate to prevent UART overrun.
- Developed `spam_stop.sh` script to rapidly send stop-monitoring commands to a device.
- Created `watch_unit.sh` script for passive monitoring of device reachability, logging results over time.

scripts/watch_unit.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+# Passive monitor for a misbehaving unit.  Every INTERVAL seconds, attempts
+# a single short TCP probe + storage_range read and logs the result.  Designed
+# to run unattended for hours/days and tell you when the unit comes back.
+#
+# Usage:
+#   ./watch_unit.sh <host> [tcp_port]
+#
+# Env:
+#   INTERVAL    Seconds between checks (default 300 = 5 min)
+#   LOG_FILE    Append results here (default /tmp/watch_<host>.log)
+#   SFM_BASE_URL  Default: http://localhost:8200
+
+set -u
+
+host="${1:-}"
+tcp_port="${2:-9034}"
+if [[ -z "$host" ]]; then
+  echo "usage: $0 <host> [tcp_port]" >&2
+  exit 2
+fi
+
+interval="${INTERVAL:-300}"
+log_file="${LOG_FILE:-/tmp/watch_${host}.log}"
+base="${SFM_BASE_URL:-http://localhost:8200}"
+
+url="${base}/device/events/storage_range?host=${host}&tcp_port=${tcp_port}"
+
+echo "watch_unit: target ${host}:${tcp_port}  interval=${interval}s  log=${log_file}"
+echo "watch_unit: Ctrl-C to stop"
+
+while true; do
+  ts=$(date '+%Y-%m-%d %H:%M:%S')
+  http_code=$(curl -sS -o /tmp/watch_resp.$$ -w "%{http_code}" \
+    --max-time 20 "$url" || echo "000")
+  body=$(cat /tmp/watch_resp.$$ 2>/dev/null || true)
+  rm -f /tmp/watch_resp.$$
+
+  case "$http_code" in
+    200|201)
+      # Strip the raw_hex for readability
+      summary=$(echo "$body" | sed 's/"raw_hex":"[^"]*",*//; s/,*$//' | head -c 200)
+      echo "$ts  REACHABLE  $summary" | tee -a "$log_file"
+      ;;
+    502|503)
+      err=$(echo "$body" | head -c 150)
+      echo "$ts  ERROR_$http_code  $err" | tee -a "$log_file"
+      ;;
+    000)
+      echo "$ts  CURL_FAIL  (network/timeout)" | tee -a "$log_file"
+      ;;
+    *)
+      echo "$ts  HTTP_$http_code  $(echo "$body" | head -c 150)" | tee -a "$log_file"
+      ;;
+  esac
+
+  sleep "$interval"
+done