Implement story 1.2: config read/write/wipe

Add provisioning/config.py with read/write/wipe functions, update
conftest.py with autouse CONFIG_PATH patch fixture, write 7 tests
covering all acceptance criteria, and extend pyproject.toml
per-file-ignores so conftest.py may import from provisioning.

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

tests/conftest.py

@@ -2,7 +2,9 @@ from pathlib import Path
 
 import pytest
 
+import planemapper.provisioning.config as config_module
 
-@pytest.fixture
-def tmp_config_path(tmp_path: Path) -> Path:
-    return tmp_path / "config.json"
+
+@pytest.fixture(autouse=True)
+def patch_config_path(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(config_module, "CONFIG_PATH", tmp_path / "config.json")

tests/provisioning/test_config.py

@@ -1,2 +1,69 @@
-def test_placeholder() -> None:
-    pass
+import json
+from pathlib import Path
+
+import pytest
+
+import planemapper.provisioning.config as config_module
+
+SAMPLE_CONFIG = {
+    "home_lat": 51.5074,
+    "home_lon": -0.1278,
+    "coverage_radius_nm": 100,
+    "wifi_ssid": "HomeNetwork",
+    "wifi_password": "s3cr3t",
+    "provisioned": False,
+}
+
+
+def test_read_raises_when_no_file_exists() -> None:
+    with pytest.raises(FileNotFoundError):
+        config_module.read()
+
+
+def test_write_creates_file_with_correct_content(tmp_path: Path) -> None:
+    config_module.write(SAMPLE_CONFIG)
+    assert config_module.CONFIG_PATH.exists()
+    with config_module.CONFIG_PATH.open() as f:
+        data = json.load(f)
+    for key in (
+        "home_lat",
+        "home_lon",
+        "coverage_radius_nm",
+        "wifi_ssid",
+        "wifi_password",
+        "provisioned",
+    ):
+        assert key in data
+    assert data["home_lat"] == 51.5074
+    assert data["wifi_ssid"] == "HomeNetwork"
+    assert data["provisioned"] is False
+
+
+def test_write_then_read_round_trips() -> None:
+    config_module.write(SAMPLE_CONFIG)
+    result = config_module.read()
+    assert result == SAMPLE_CONFIG
+
+
+def test_wipe_deletes_file() -> None:
+    config_module.write(SAMPLE_CONFIG)
+    assert config_module.CONFIG_PATH.exists()
+    config_module.wipe()
+    assert not config_module.CONFIG_PATH.exists()
+
+
+def test_wipe_then_read_raises() -> None:
+    config_module.write(SAMPLE_CONFIG)
+    config_module.wipe()
+    with pytest.raises(FileNotFoundError):
+        config_module.read()
+
+
+def test_wipe_is_idempotent() -> None:
+    # wipe on a non-existent file should not raise
+    config_module.wipe()
+    config_module.wipe()
+
+
+def test_config_path_is_in_tmp_path(tmp_path: Path) -> None:
+    assert str(config_module.CONFIG_PATH).startswith(str(tmp_path))