feat: plex EAE watchdog and plex_eae_failure pattern

Add plex_eae_failure pattern to default.yaml targeting the EasyAudioEncoder
crash signature (EAE timeout + I/O error pair, 5s cadence). Pattern fires
when EAE's WAV handoff files stop appearing in the pms temp directory.

Add watch_plex.py: tail-based watchdog that counts EAE timeout events and
auto-restarts plexmediaserver after N consecutive hits (default 3, ~15s of
failure). Includes cooldown, dry-run mode, and a systemd unit template.

patterns/default.yaml

@@ -82,6 +82,12 @@ patterns:
     description: IP address change or DHCP event
 
   # Add device/service-specific patterns below this line:
+
+  - name: plex_eae_failure
+    pattern: "(EAE timeout|EAE not running|eac3_eae.*error reading output|Error submitting packet to decoder.*I/O error)"
+    severity: ERROR
+    description: Plex EasyAudioEncoder (EAC3 Dolby audio transcoder) crashed — service restart required
+
   # - name: avcx_device_error
   #   pattern: "ERR-\d{4}"
   #   severity: ERROR

scripts/watch_plex.py

@@ -0,0 +1,136 @@
+"""Watchdog: detect Plex EAE (EasyAudioEncoder) failures and auto-restart.
+
+The EAE daemon handles Dolby EAC3/DDP audio transcoding. When it crashes,
+Plex logs 'EAE timeout!' at 5-second intervals until the service is restarted.
+
+Run as root or a user with `systemctl restart plexmediaserver` permission.
+
+Usage:
+    python scripts/watch_plex.py [--log PATH] [--threshold N] [--cooldown SECS] [--dry-run]
+
+Systemd unit (deploy to /etc/systemd/system/turnstone-plex-watchdog.service):
+    [Unit]
+    Description=Turnstone Plex EAE watchdog
+    After=plexmediaserver.service
+
+    [Service]
+    ExecStart=/usr/bin/python3 /opt/turnstone/scripts/watch_plex.py
+    Restart=always
+    RestartSec=10
+
+    [Install]
+    WantedBy=multi-user.target
+"""
+from __future__ import annotations
+
+import argparse
+import logging
+import subprocess
+import sys
+import time
+from pathlib import Path
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s %(levelname)s %(message)s",
+    datefmt="%Y-%m-%d %H:%M:%S",
+)
+logger = logging.getLogger("plex-watchdog")
+
+DEFAULT_LOG = Path(
+    "/var/lib/plexmediaserver/Library/Application Support"
+    "/Plex Media Server/Logs/Plex Media Server.log"
+)
+EAE_TRIGGER = "EAE timeout!"
+SERVICE = "plexmediaserver"
+
+
+def _restart(dry_run: bool) -> bool:
+    cmd = ["systemctl", "restart", SERVICE]
+    if dry_run:
+        logger.info("[dry-run] would run: %s", " ".join(cmd))
+        return True
+    result = subprocess.run(cmd, capture_output=True, text=True)
+    if result.returncode == 0:
+        logger.info("Restart successful")
+        return True
+    logger.error("Restart failed (exit %d): %s", result.returncode, result.stderr.strip())
+    return False
+
+
+def _tail_f(path: Path):
+    """Yield new lines from a growing log file, blocking between reads."""
+    with open(path, errors="replace") as f:
+        f.seek(0, 2)  # start at end — don't replay history on startup
+        while True:
+            line = f.readline()
+            if line:
+                yield line
+            else:
+                time.sleep(0.25)
+
+
+def watch(log_path: Path, threshold: int, cooldown: int, dry_run: bool) -> None:
+    logger.info(
+        "Watching %s | threshold=%d EAE timeouts | cooldown=%ds%s",
+        log_path, threshold, cooldown, " | DRY RUN" if dry_run else "",
+    )
+
+    eae_count = 0
+    last_restart: float = 0.0
+
+    for line in _tail_f(log_path):
+        line = line.strip()
+
+        if "Started plexmediaserver" in line or "Starting plexmediaserver" in line:
+            if eae_count > 0:
+                logger.info("Service (re)started — resetting EAE counter")
+            eae_count = 0
+            continue
+
+        if EAE_TRIGGER not in line:
+            continue
+
+        eae_count += 1
+        logger.warning("EAE timeout #%d detected", eae_count)
+
+        if eae_count < threshold:
+            continue
+
+        now = time.time()
+        remaining = cooldown - (now - last_restart)
+        if remaining > 0:
+            logger.warning(
+                "Threshold reached but cooldown active (%.0fs remaining) — skipping restart",
+                remaining,
+            )
+            continue
+
+        logger.error(
+            "EAE failure confirmed (%d timeouts) — restarting %s", eae_count, SERVICE
+        )
+        if _restart(dry_run):
+            last_restart = now
+        eae_count = 0
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description="Plex EAE watchdog")
+    parser.add_argument("--log", type=Path, default=DEFAULT_LOG, help="Plex server log path")
+    parser.add_argument("--threshold", type=int, default=3, help="EAE timeouts before restart (default 3)")
+    parser.add_argument("--cooldown", type=int, default=300, help="Seconds between restarts (default 300)")
+    parser.add_argument("--dry-run", action="store_true", help="Log what would happen without restarting")
+    args = parser.parse_args()
+
+    if not args.log.exists():
+        logger.error("Log file not found: %s", args.log)
+        sys.exit(1)
+
+    try:
+        watch(args.log, args.threshold, args.cooldown, args.dry_run)
+    except KeyboardInterrupt:
+        logger.info("Watchdog stopped")
+
+
+if __name__ == "__main__":
+    main()