Gate uploads on a built firmware, refuse unclaimed native builds, seed the CI toolchain cache from dev

The upload path now checks CORE.firmware_bin exists before invoking
esptool and names the fix (compile first) instead of failing inside
esptool. compile_program raises when a native toolchain resolved but no
platform backend claimed the build rather than falling through to a
mis-configured PlatformIO project. The addr2line failure warning now
includes the exception so the cause is visible without debug logging.

CI: the native toolchain cache is restore-only on PRs and seeded by a
new dev-push job, mirroring seed-apt-cache; the key resolves the pinned
core and toolchain versions from code instead of hashing framework.py.
determine-jobs main() output tests now pin the esp8266_native pair.

tests/script/test_determine_jobs.py

@@ -78,6 +78,17 @@ def mock_esp32_platformio_components_to_test() -> Generator[Mock, None, None]:
         yield mock
 
 
+@pytest.fixture
+def mock_esp8266_native_components_to_test() -> Generator[Mock, None, None]:
+    """Mock esp8266_native_components_to_test from determine_jobs.
+
+    main() drives both the ``esp8266_native`` boolean output and the
+    ``esp8266_native_components`` CSV from this one function.
+    """
+    with patch.object(determine_jobs, "esp8266_native_components_to_test") as mock:
+        yield mock
+
+
 @pytest.fixture
 def mock_determine_cpp_unit_tests() -> Generator[Mock, None, None]:
     """Mock determine_cpp_unit_tests from helpers."""
@@ -116,6 +127,7 @@ def test_main_all_tests_should_run(
     mock_should_run_import_time: Mock,
     mock_should_run_device_builder: Mock,
     mock_esp32_platformio_components_to_test: Mock,
+    mock_esp8266_native_components_to_test: Mock,
     mock_changed_files: Mock,
     mock_determine_cpp_unit_tests: Mock,
     capsys: pytest.CaptureFixture[str],
@@ -132,6 +144,7 @@ def test_main_all_tests_should_run(
     mock_should_run_import_time.return_value = True
     mock_should_run_device_builder.return_value = True
     mock_esp32_platformio_components_to_test.return_value = ["api", "esp32"]
+    mock_esp8266_native_components_to_test.return_value = ["api", "logger"]
     mock_determine_cpp_unit_tests.return_value = (False, ["wifi", "api", "sensor"])
 
     # Mock changed_files to return non-component files (to avoid memory impact)
@@ -215,6 +228,8 @@ def test_main_all_tests_should_run(
     assert output["device_builder"] is True
     assert output["esp32_platformio"] is True
     assert output["esp32_platformio_components"] == "api,esp32"
+    assert output["esp8266_native"] is True
+    assert output["esp8266_native_components"] == "api,logger"
     assert output["changed_components"] == ["wifi", "api", "sensor"]
     # changed_components_with_tests will only include components that actually have test files
     assert "changed_components_with_tests" in output
@@ -251,6 +266,7 @@ def test_main_no_tests_should_run(
     mock_should_run_import_time: Mock,
     mock_should_run_device_builder: Mock,
     mock_esp32_platformio_components_to_test: Mock,
+    mock_esp8266_native_components_to_test: Mock,
     mock_changed_files: Mock,
     mock_determine_cpp_unit_tests: Mock,
     capsys: pytest.CaptureFixture[str],
@@ -267,6 +283,7 @@ def test_main_no_tests_should_run(
     mock_should_run_import_time.return_value = False
     mock_should_run_device_builder.return_value = False
     mock_esp32_platformio_components_to_test.return_value = []
+    mock_esp8266_native_components_to_test.return_value = []
     mock_determine_cpp_unit_tests.return_value = (False, [])
 
     # Mock changed_files to return no component files
@@ -309,6 +326,8 @@ def test_main_no_tests_should_run(
     assert output["device_builder"] is False
     assert output["esp32_platformio"] is False
     assert output["esp32_platformio_components"] == ""
+    assert output["esp8266_native"] is False
+    assert output["esp8266_native_components"] == ""
     assert output["changed_components"] == []
     assert output["changed_components_with_tests"] == []
     assert output["component_test_count"] == 0

tests/unit_tests/test_main.py

@@ -7139,6 +7139,8 @@ def test_upload_using_esptool_arduino_toolchain(
     """The native ESP8266 Arduino toolchain flashes CORE.firmware_bin at 0x0."""
     setup_core(platform=PLATFORM_ESP8266, tmp_path=tmp_path, name="test")
     CORE.toolchain = Toolchain.ARDUINO
+    CORE.firmware_bin.parent.mkdir(parents=True, exist_ok=True)
+    CORE.firmware_bin.touch()
 
     config = {CONF_ESPHOME: {"platformio_options": {}}}
     result = upload_using_esptool(config, "/dev/ttyUSB0", None, None)
@@ -7404,3 +7406,26 @@ def test_cli_toolchain_skips_the_validated_config_cache(tmp_path: Path) -> None:
         assert run_esphome(argv) == 2
     mock_cache.assert_not_called()
     mock_read.assert_called_once()
+
+
+def test_upload_using_esptool_native_missing_firmware_raises(
+    tmp_path: Path,
+) -> None:
+    """A stale or absent firmware.bin fails by name instead of flashing air."""
+    setup_core(platform=PLATFORM_ESP8266, tmp_path=tmp_path, name="test")
+    CORE.toolchain = Toolchain.ARDUINO
+    with pytest.raises(EsphomeError, match="compile the configuration first"):
+        upload_using_esptool(
+            {CONF_ESPHOME: {"platformio_options": {}}}, "/dev/ttyUSB0", None, None
+        )
+
+
+def test_compile_program_unclaimed_native_toolchain_raises(
+    tmp_path: Path,
+) -> None:
+    """A resolved native toolchain no platform backend claims must fail,
+    never fall through to the PlatformIO project path."""
+    setup_core(platform=PLATFORM_ESP32, tmp_path=tmp_path, name="test_device")
+    CORE.toolchain = Toolchain.ARDUINO  # esp32 has no arduino-native backend
+    with pytest.raises(EsphomeError, match="no platform backend claimed"):
+        compile_program(MockArgs(), {})