Guard the session start against a missing key, reword the warning, and let the wizard use the key for OTA

tests/unit_tests/test_wizard.py

@@ -101,6 +101,25 @@ def test_config_file_should_include_ota(default_config: dict[str, Any]):
     assert "ota:" in config
 
 
+def test_config_file_should_use_encryption_when_api_key_set(
+    default_config: dict[str, Any],
+):
+    """
+    With an API encryption key and no OTA password the OTA block reuses the key
+    """
+    # Given
+    default_config["api_encryption_key"] = (
+        "AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8="
+    )
+
+    # When
+    config = wz.wizard_file(**default_config)
+
+    # Then
+    assert "ota:\n  - platform: esphome\n    encryption:" in config
+    assert "password" not in config.split("ota:")[1].split("wifi:")[0]
+
+
 def test_config_file_should_include_ota_when_password_set(
     default_config: dict[str, Any],
 ):