test(ci): F4 — entity-contract pass in the drift sweep + real-HA state-write proof (t40)

The F1 blocker was invisible to every existing test: the stub harnesses call the
entity and replace ``async_write_ha_state``, so a non-property
``extra_state_attributes`` looked perfectly healthy. Two new gates close that
hole.

1. ``ha_api_drift.scan_entity_contracts()`` — a pure-AST pass (so it needs no
   homeassistant, unlike passes 1-3) that walks every class inheriting from an
   HA entity base, including our own intermediate ``NvidiaShieldSensorBase``, and
   flags any HA-READ attribute (``extra_state_attributes``, ``available``,
   ``state``, ``native_value``, ``media_*``, …) declared as a plain method
   instead of ``@property``. It is wired into ``scan()`` before the
   homeassistant gate and exported for the fast suite, so ONE implementation
   backs the sweep, the CLI red proof and tests/test_entity_contract.py (the t39
   F1 lesson).
   Red proof on the pre-fix tree:
     media_player.py:828: entity-attribute-is-a-method:
     NvidiaShieldMediaPlayer.extra_state_attributes is a plain method, but HA
     reads it as an attribute (``attr |= self.<name>``) — declare it @property
   …and HEAD is clean (13 modules, 60 imports, 35 call arguments, 7 awaited).

2. tests/test_ha_api_drift.py now builds each entity under REAL homeassistant
   (real ``PlatformData``, real ``async_write_ha_state``) and asserts HA's own
   ``__async_calculate_state`` succeeds and that the media player's app_id/
   app_name survive the merge — for the media player, both sensors, the remote
   and the pairing button. A coverage test compares that matrix against the
   sweep's classification, so a new entity class cannot quietly skip it.

Verified: 296 passed / 2 skipped (fast suite), 16 passed (drift suite under
Python 3.14 + homeassistant 2026.10.1), ruff clean; the entity-contract red
proof above reproduces exactly the reported line.

tests/test_ha_api_drift.py

@@ -12,9 +12,12 @@ The sweep itself lives in ``tests/ha_api_drift.py`` (documented there).
 from __future__ import annotations
 
 import ast
+import importlib
 import subprocess
 import sys
+import threading
 from pathlib import Path
+from types import SimpleNamespace
 
 import ha_api_drift
 import pytest
@@ -206,3 +209,152 @@ def test_the_declared_python_floor_never_lags_homeassistant():
         f"but the installed homeassistant requires {declared} — raise the constant "
         f"and the setup-python version in .gitea/workflows/test.yml"
     )
+
+
+# ------------------------------------------------- entity contract (t40, real HA)
+#
+# The stub suites cannot see this class of defect: their harness replaces
+# ``async_write_ha_state``, so a non-property ``extra_state_attributes`` looks
+# fine there. Only HA's own ``Entity.__async_calculate_state`` — which does
+# ``attr |= self.extra_state_attributes`` — turns it into
+# ``TypeError: 'method' object is not iterable`` and stops the entity from ever
+# rendering. These tests drive that real path.
+
+_REPO_ROOT = Path(__file__).resolve().parent.parent
+
+
+class _RecordingStates:
+    """Minimal ``hass.states``: keeps what HA's entity writes."""
+
+    def __init__(self):
+        self.registry: dict = {}
+        self.written: list = []
+
+    def get(self, entity_id):
+        return self.registry.get(entity_id)
+
+    def async_set_internal(self, entity_id, state, attr, *args):
+        self.written.append((entity_id, state, dict(attr)))
+
+
+def _real_ha_entity(module_name, class_name, *, options=None, entity_id=None):
+    """Build a production entity under real homeassistant (no platform)."""
+    if str(_REPO_ROOT) not in sys.path:
+        sys.path.insert(0, str(_REPO_ROOT))
+    module = importlib.import_module(f"custom_components.nvidia_shield.{module_name}")
+    states = _RecordingStates()
+    hass = SimpleNamespace(
+        loop_thread_id=threading.get_ident(),
+        states=states,
+        data={},
+        config=SimpleNamespace(components=set()),
+    )
+    entry = SimpleNamespace(
+        entry_id="e1", data={}, options=dict(options or {}), title="Shield"
+    )
+    entity = getattr(module, class_name)(hass, entry)
+    entity.entity_id = entity_id
+    # HA's real translation-key paths (``unit_of_measurement``, device-class
+    # names) need the platform's translation data; without it a translation-keyed
+    # entity raises "cannot have a translation key ... before being added to the
+    # entity platform". PlatformData is the real container, so the entity is
+    # exercised with the same shape it sees in production.
+    from homeassistant.helpers.entity_platform import PlatformData
+
+    entity.platform_data = PlatformData(
+        hass, domain=module_name, platform_name="nvidia_shield"
+    )
+    # Not added through an EntityComponent: HA would warn once via
+    # _suggest_report_issue (which needs hass.data["integrations"]) — set the
+    # flag it uses to report that once instead of faking a whole platform.
+    entity._no_platform_reported = True
+    return entity, states
+
+
+def _write_ha_state(entity, states):
+    """Run HA's real state write and return what reached the state machine."""
+    entity.async_write_ha_state()
+    assert states.written, f"{type(entity).__name__} wrote no state"
+    return states.written[-1]
+
+
+#: Every concrete entity class in the integration, exercised above against the
+#: REAL state machine. t40: the media player's defect was a state-write crash, so
+#: "the whole tree renders" is the contract under test, not a single entity.
+_REAL_HA_MATRIX = (
+    ("media_player", "NvidiaShieldMediaPlayer", None, "media_player.shield"),
+    ("sensor", "NvidiaShieldCurrentAppSensor", None, "sensor.shield_current_app"),
+    (
+        "sensor",
+        "NvidiaShieldNowPlayingSensor",
+        {"jellyfin_entity": "media_player.jellyfin"},
+        "sensor.shield_now_playing",
+    ),
+    ("remote", "NvidiaShieldRemoteEntity", None, "remote.shield"),
+    ("button", "NvidiaShieldPairAdbButton", None, "button.shield_pair_adb"),
+)
+
+#: Classified as an entity by the sweep, but an abstract intermediate base HA
+#: never instantiates — its concrete subclasses are in the matrix.
+_INTERMEDIATE_BASES = frozenset({"NvidiaShieldSensorBase"})
+
+
+@pytest.mark.parametrize(
+    ("module_name", "class_name", "options", "entity_id"), _REAL_HA_MATRIX
+)
+def test_entities_calculate_state_under_real_homeassistant(
+    module_name, class_name, options, entity_id
+):
+    """t40 blocker: HA's own state write must not raise for ANY entity.
+
+    ``Entity.async_write_ha_state`` → ``__async_calculate_state`` merges the
+    extra attributes with ``attr |= ...``; the pre-fix media player raised
+    ``TypeError: 'method' object is not iterable`` here, so it could never render.
+    """
+    _require_installed_homeassistant()
+
+    entity, states = _real_ha_entity(
+        module_name, class_name, options=options, entity_id=entity_id
+    )
+
+    written_id, state, attrs = _write_ha_state(entity, states)
+
+    assert written_id == entity_id
+    assert isinstance(state, str)
+    assert isinstance(attrs, dict)
+
+
+def test_the_media_player_extra_attributes_reach_the_state_machine():
+    """The property's payload must survive HA's merge, not merely not raise."""
+    _require_installed_homeassistant()
+
+    entity, states = _real_ha_entity(
+        "media_player", "NvidiaShieldMediaPlayer", entity_id="media_player.shield"
+    )
+
+    _entity_id, _state, attrs = _write_ha_state(entity, states)
+
+    assert {"app_id", "app_name"} <= set(attrs), sorted(attrs)
+
+
+def test_the_real_ha_matrix_covers_every_entity_class_in_the_tree():
+    """A new entity class must join the matrix above, or this test fails.
+
+    The sweep classifies entities from the AST; this keeps the real-HA coverage
+    in step with that classification instead of silently shrinking.
+    """
+    _require_installed_homeassistant()
+
+    classified: set[str] = set()
+    for path in sorted(ha_api_drift.SHIELD_DIR.glob("*.py")):
+        classified |= ha_api_drift.entity_class_names(
+            ast.parse(path.read_text(encoding="utf-8"))
+        )
+    covered = {class_name for _module, class_name, _options, _entity_id in _REAL_HA_MATRIX}
+
+    uncovered = classified - covered - _INTERMEDIATE_BASES
+
+    assert uncovered == set(), (
+        f"entity classes never exercised against real HA: {sorted(uncovered)} — "
+        f"add them to _REAL_HA_MATRIX"
+    )