Platform adapter: rename System_Essentials, add Plugin/unraid/adapter.sh, wire call sites

- Rename unRAID_Essentials/ → System_Essentials/ (git detects as rename)
- Add Plugin/unraid/adapter.sh: 13 platform_*() functions providing OS-agnostic API
  for storage health, service management, mover, user scripts, notifications,
  disk temps, and platform command validation
- Update load_config.sh: detect PLATFORM (unraid/truenas/unknown), export SCRIPTS_DIR,
  auto-source Plugin/$PLATFORM/adapter.sh after common.sh
- Wire all call sites: replace direct rc.d, pgrep/pkill, var.ini, dynamix.cfg,
  disks.ini, and validate_unraid_cmd calls with platform_*() functions across
  watchdogs, orchestrators, and System_Essentials scripts
- Update all documentation: rename refs, update webgui escalation logic,
  add platform adapter section to Plugin README, update main README with
  portability vision and corrected self-healing stack description

Watchdogs/docker_watchdog.sh

@@ -256,9 +256,9 @@ log "$ICON_CONTAINERS Tier1:  watched=${#WATCHDOG_CONTAINERS[@]} required=${#WAT
 
 # Validate unRAID-specific commands used by this script
 # If rc.docker is missing or changed, daemon restart will fail — better to know now
-validate_unraid_cmd     "/etc/rc.d/rc.docker"     ""     ""     "Docker rc.d script" || warn "rc.docker not found — daemon restart unavailable if needed"
+platform_require_cmd     "/etc/rc.d/rc.docker"     ""     ""     "Docker rc.d script" || warn "rc.docker not found — daemon restart unavailable if needed"
 
-validate_unraid_cmd     "/usr/local/emhttp/plugins/dynamix/scripts/notify"     ""     ""     "unRAID notify script" || warn "unRAID notify script not found — native notifications disabled"
+platform_require_cmd     "/usr/local/emhttp/plugins/dynamix/scripts/notify"     ""     ""     "unRAID notify script" || warn "unRAID notify script not found — native notifications disabled"
 
 # Ensure state files exist
 touch "$WATCHDOG_STATE_FILE" "$WATCHDOG_CONTAINER_RESTART_LOG" \
@@ -453,15 +453,8 @@ flush_notify() {
     NOTIFY_EVENTS=()
 }
 
-# Returns 0 if parity check is currently running
-# Unraid 7.3+: mdResync in var.ini (non-zero = check/sync in progress)
-# Older: parity-date.txt contained "progress" — check both for compatibility
-is_parity_running() {
-    local resync
-    resync=$(awk -F'"' '/^mdResync=/{print $2}' /var/local/emhttp/var.ini 2>/dev/null)
-    [[ -n "$resync" && "$resync" != "0" ]] && return 0
-    grep -q "progress" /var/local/emhttp/parity-date.txt 2>/dev/null
-}
+# is_parity_running — delegates to adapter
+is_parity_running() { platform_is_maintenance_running; }
 
 # ==============================================================================================
 # ── DOCKER DAEMON HEALTH CHECK ────────────────────────────────────────────────────────────────
@@ -567,16 +560,14 @@ check_docker_daemon() {
     notify "Docker daemon hung on $(hostname) — attempting restart" "Docker Watchdog" "warning"
 
     if [[ "$DRY_RUN" == true ]]; then
-        warn "DRY RUN — would restart Docker daemon via /etc/rc.d/rc.docker restart"
+        warn "DRY RUN — would restart Docker daemon via platform_restart_service docker"
         return 1
     fi
 
-    # Restart daemon — unRAID uses rc.d scripts, not systemd
-    # timeout 180: rc.docker stops all containers before restarting — without a limit this
-    # can block for 30+ min on a busy host, holding the orchestrator lock the entire time.
+    # timeout 180: Docker daemon stop can block for 30+ min on a busy host.
     WATCHDOG_DAEMON_RESTARTED=true
     set_strikes "daemon_restarted_flag" "true" "$WATCHDOG_STATE_FILE"
-    if timeout 180 /etc/rc.d/rc.docker restart >/dev/null 2>&1; then
+    if timeout 180 platform_restart_service docker; then
         log "Docker daemon restart issued — waiting ${WATCHDOG_DAEMON_RESTART_WAIT}s..."
         sleep "$WATCHDOG_DAEMON_RESTART_WAIT"
 
@@ -598,8 +589,8 @@ check_docker_daemon() {
             return 1
         fi
     else
-        # rc.docker not found or failed — flag immediately, stability_watchdog escalates
-        error "Failed to issue Docker daemon restart — /etc/rc.d/rc.docker not found or failed"
+        # platform_restart_service returned non-zero — flag immediately, stability_watchdog escalates
+        error "Failed to issue Docker daemon restart — platform_restart_service docker failed"
         set_strikes "daemon_confirmed_down" "true" "$WATCHDOG_STATE_FILE"
         queue_notify "Docker daemon restart command failed on $(hostname) — stability_watchdog escalating" "critical"
         flush_notify
@@ -632,7 +623,6 @@ CYCLE_START=$(date +%s)
     done
 
     # ── Skip list visibility ─────────────────────────────────────────────────────────────────
-    local _skip_contents
     _skip_contents=$(cat "$DOCKER_WATCHDOG_FAILED_FILE" 2>/dev/null | tr '\n' ' ' | xargs)
     [[ -n "$_skip_contents" ]] && warn "$ICON_SKIP Skip list active: $_skip_contents — manual intervention needed"