feat(simulator): virtual drone fleet data generator

One process per drone: seeded patrol kinematics, sensor streams at
realistic rates, detection events, hot current/ blocks sealed into
Hive-partitioned Parquet, and the compact UDP state broadcast with
peer RSSI derivation. Scales via docker compose --scale.

simulator/virtual_drone/broadcast.py

@@ -0,0 +1,68 @@
+"""State broadcast over UDP: the compact pose frame from the sync design.
+
+Frame layout (little-endian, 46 bytes):
+
+    magic     2s   b"SH"
+    version   B
+    drone_id  8s   zero-padded ascii
+    ts_ns     q    epoch nanoseconds
+    pos_mm    3i   position, millimeters (quantized on the wire only)
+    att_cdeg  3h   roll/pitch/yaw, centi-degrees
+    vel_cms   3h   velocity, cm/s
+    frame_ref B
+    flags     B
+"""
+
+from __future__ import annotations
+
+import socket
+import struct
+from typing import Any
+
+from .flight import Pose
+
+FRAME = struct.Struct("<2sB8sq3i3h3hBB")
+MAGIC = b"SH"
+VERSION = 1
+
+
+def encode_state(drone_id: str, pose: Pose, flags: int = 0) -> bytes:
+    return FRAME.pack(
+        MAGIC,
+        VERSION,
+        drone_id.encode()[:8].ljust(8, b"\0"),
+        pose.ts_ns,
+        int(pose.x * 1000), int(pose.y * 1000), int(pose.z * 1000),
+        int(pose.roll * 100), int(pose.pitch * 100), int(pose.yaw * 100),
+        int(pose.vx * 100), int(pose.vy * 100), int(pose.vz * 100),
+        0,
+        flags,
+    )
+
+
+def decode_state(payload: bytes) -> dict[str, Any] | None:
+    if len(payload) != FRAME.size:
+        return None
+    magic, version, drone_id, ts_ns, px, py, pz, r, p, y, vx, vy, vz, frame_ref, flags = FRAME.unpack(payload)
+    if magic != MAGIC or version != VERSION:
+        return None
+    return {
+        "ts_ns": ts_ns,
+        "peer_id": drone_id.rstrip(b"\0").decode(),
+        "pos_x": px / 1000.0, "pos_y": py / 1000.0, "pos_z": pz / 1000.0,
+        "roll": r / 100.0, "pitch": p / 100.0, "yaw": y / 100.0,
+        "vel_x": vx / 100.0, "vel_y": vy / 100.0, "vel_z": vz / 100.0,
+        "frame_ref": frame_ref,
+        "flags": flags,
+    }
+
+
+def open_socket(port: int) -> socket.socket:
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    if hasattr(socket, "SO_REUSEPORT"):
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+    sock.bind(("", port))
+    sock.setblocking(False)
+    return sock