feat: Add mDNS, watchdog, human-readable uptime, esp-fleet tool

Firmware:
- mDNS announcement as <hostname>.local (configurable via Kconfig)
- Task watchdog with 30s timeout and auto-reboot on hang
- STATUS now returns human-readable uptime (e.g., 3d2h15m) and hostname

Pi-side tools:
- esp-cmd: mDNS hostname resolution (esp-cmd amber-maple.local STATUS)
- esp-fleet: parallel command to all sensors (esp-fleet status)

Tested on amber-maple — mDNS resolves, watchdog active, fleet tool works.

tools/esp-cmd

@@ -8,7 +8,9 @@ DEFAULT_PORT = 5501
 TIMEOUT = 2.0
 
 USAGE = """\
-Usage: esp-cmd <ip> <command> [args...]
+Usage: esp-cmd <host> <command> [args...]
+
+Host can be an IP address or mDNS hostname (e.g., amber-maple.local).
 
 Commands:
   STATUS              Query device state (uptime, heap, RSSI, tx_power, rate)
@@ -18,11 +20,19 @@ Commands:
   POWER <2-20>        Set TX power in dBm (saved to NVS)
 
 Examples:
-  esp-cmd 192.168.1.50 STATUS
-  esp-cmd 192.168.1.50 RATE 50
-  esp-cmd 192.168.1.50 POWER 10
-  esp-cmd 192.168.1.50 REBOOT
-  esp-cmd 192.168.1.50 IDENTIFY"""
+  esp-cmd amber-maple.local STATUS
+  esp-cmd 192.168.129.30 RATE 50
+  esp-cmd amber-maple.local IDENTIFY"""
+
+
+def resolve(host):
+    """Resolve hostname to IP address (supports mDNS .local)."""
+    try:
+        result = socket.getaddrinfo(host, DEFAULT_PORT, socket.AF_INET, socket.SOCK_DGRAM)
+        return result[0][4][0]
+    except socket.gaierror as e:
+        print(f"ERR: cannot resolve {host}: {e}", file=sys.stderr)
+        sys.exit(1)
 
 
 def main():
@@ -30,8 +40,9 @@ def main():
         print(USAGE)
         sys.exit(0 if sys.argv[1:] and sys.argv[1] in ("-h", "--help") else 2)
 
-    ip = sys.argv[1]
+    host = sys.argv[1]
     cmd = " ".join(sys.argv[2:]).strip()
+    ip = resolve(host)
 
     sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
     sock.settimeout(TIMEOUT)
@@ -41,7 +52,7 @@ def main():
         data, _ = sock.recvfrom(512)
         print(data.decode().strip())
     except socket.timeout:
-        print(f"ERR: no reply from {ip}:{DEFAULT_PORT} (timeout {TIMEOUT}s)", file=sys.stderr)
+        print(f"ERR: no reply from {host} ({ip}:{DEFAULT_PORT}), timeout {TIMEOUT}s", file=sys.stderr)
         sys.exit(1)
     except OSError as e:
         print(f"ERR: {e}", file=sys.stderr)

tools/esp-fleet

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+"""Query all ESP32 CSI sensors in parallel."""
+
+import concurrent.futures
+import socket
+import sys
+
+DEFAULT_PORT = 5501
+TIMEOUT = 2.0
+
+SENSORS = [
+    ("muddy-storm",  "muddy-storm.local"),
+    ("amber-maple",  "amber-maple.local"),
+    ("hollow-acorn", "hollow-acorn.local"),
+]
+
+USAGE = """\
+Usage: esp-fleet <command> [args...]
+
+Sends a command to all known sensors in parallel and prints results.
+
+Commands:
+  status              Query all devices
+  identify            Blink LEDs on all devices
+  rate <10-100>       Set ping rate on all devices
+  power <2-20>        Set TX power on all devices
+  reboot              Reboot all devices
+
+Examples:
+  esp-fleet status
+  esp-fleet identify
+  esp-fleet rate 50"""
+
+
+def query(name, host, cmd):
+    """Send command to one sensor, return (name, reply_or_error)."""
+    try:
+        info = socket.getaddrinfo(host, DEFAULT_PORT, socket.AF_INET, socket.SOCK_DGRAM)
+        ip = info[0][4][0]
+    except socket.gaierror:
+        return (name, f"ERR: cannot resolve {host}")
+
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    sock.settimeout(TIMEOUT)
+    try:
+        sock.sendto(cmd.encode(), (ip, DEFAULT_PORT))
+        data, _ = sock.recvfrom(512)
+        return (name, data.decode().strip())
+    except socket.timeout:
+        return (name, f"ERR: timeout ({ip})")
+    except OSError as e:
+        return (name, f"ERR: {e}")
+    finally:
+        sock.close()
+
+
+def main():
+    if len(sys.argv) < 2 or sys.argv[1] in ("-h", "--help"):
+        print(USAGE)
+        sys.exit(0 if sys.argv[1:] and sys.argv[1] in ("-h", "--help") else 2)
+
+    cmd = " ".join(sys.argv[1:]).strip().upper()
+
+    with concurrent.futures.ThreadPoolExecutor(max_workers=len(SENSORS)) as pool:
+        futures = {pool.submit(query, name, host, cmd): name for name, host in SENSORS}
+        results = {}
+        for f in concurrent.futures.as_completed(futures):
+            name, reply = f.result()
+            results[name] = reply
+
+    # Print in sensor order
+    max_name = max(len(n) for n, _ in SENSORS)
+    for name, _ in SENSORS:
+        print(f"{name:<{max_name}}  {results[name]}")
+
+
+if __name__ == "__main__":
+    main()