QA: add structural and model tests for story 1.1 scaffold

Replaces placeholder stubs in test_models.py, test_gpio_ctrl.py, and
provisioning/test_provision_loop.py with real assertions. Adds new
test_scaffold.py covering AC3 file-presence, importlib.resources
airports.csv load, constants completeness, and main.py provisioning
import guard. Extends ruff per-file-ignores so tests/provisioning/*.py
may import from planemapper.provisioning. All 22 tests pass; ruff
check and format --check both clean.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_models.py

@@ -1,2 +1,28 @@
-def test_placeholder() -> None:
-    pass
+from planemapper.models import Aircraft
+
+
+def test_aircraft_defaults() -> None:
+    a = Aircraft(icao="ABC123", lat=51.5, lon=-0.1)
+    assert a.heading == 0.0
+    assert a.altitude_ft == 0
+    assert a.callsign == ""
+    assert a.category == ""
+    assert a.is_mlat is False
+    assert a.is_stale is False
+
+
+def test_aircraft_full() -> None:
+    a = Aircraft(
+        icao="ABC123",
+        lat=51.5,
+        lon=-0.1,
+        heading=90.0,
+        altitude_ft=5000,
+        callsign="BAW1",
+        category="A3",
+        is_mlat=True,
+        is_stale=False,
+    )
+    assert a.heading == 90.0
+    assert a.callsign == "BAW1"
+    assert a.is_mlat is True