test: add pytest suite and gate Docker builds on it

Unit tests cover the SQL gate, broadcast codec, Hive writer layout,
and flight kinematics. CI runs pytest first; the simulator image build
runs tests in a dedicated stage before the final layer.

simulator/tests/test_flight.py

@@ -0,0 +1,35 @@
+"""Flight kinematics — waypoint patrol and step integration."""
+
+from __future__ import annotations
+
+import random
+
+from virtual_drone.config import Config
+from virtual_drone.flight import initial_pose, make_waypoints, step
+
+
+def test_make_waypoints_returns_closed_perimeter() -> None:
+    cfg = Config()
+    rng = random.Random(7)
+    wps = make_waypoints(cfg, rng)
+    assert len(wps) == 4
+    assert all(len(p) == 2 for p in wps)
+
+
+def test_step_moves_toward_target() -> None:
+    cfg = Config()
+    rng = random.Random(3)
+    pose = initial_pose(cfg, rng, 1_000_000_000)
+    target = (pose.x + 50.0, pose.y + 50.0)
+    next_pose, _ = step(pose, target, cfg, rng, dt=0.1, ts_ns=1_100_000_000)
+    dist_before = ((target[0] - pose.x) ** 2 + (target[1] - pose.y) ** 2) ** 0.5
+    dist_after = ((target[0] - next_pose.x) ** 2 + (target[1] - next_pose.y) ** 2) ** 0.5
+    assert dist_after < dist_before
+
+
+def test_reached_when_close_to_waypoint() -> None:
+    cfg = Config()
+    rng = random.Random(1)
+    pose = initial_pose(cfg, rng, 2_000_000_000)
+    _, reached = step(pose, (pose.x, pose.y), cfg, rng, dt=1.0, ts_ns=2_100_000_000)
+    assert reached is True