chore: repo scaffold, Apache-2.0, test harness, CI workflows

Local pytest execution is skipped by owner decision: no release of
pytest-homeassistant-custom-component that pins a Home Assistant
2026.9.x floor installs on Python 3.13 (0.13.317+ requires Python
3.14, which this workstation does not have). requirements_test.txt
is pinned to the correct >=0.13.317 range for CI (Python 3.14) and
files are validated with py_compile instead of a local pytest run.

CI workflows (test.yaml, validate.yaml) moved forward from a later
task since, with local testing gone, CI is the only gate and must
exist before the code it gates.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01739Seac5eMAfNwFeiwV5r4

tests/conftest.py

@@ -0,0 +1,11 @@
+"""Fixtures for openai_compatible tests."""
+
+import pytest
+
+pytest_plugins = "pytest_homeassistant_custom_component"
+
+
+@pytest.fixture(autouse=True)
+def auto_enable_custom_integrations(enable_custom_integrations):
+    """Enable loading custom integrations in all tests."""
+    return