fix(drift): F1+F2 — the sweep refuses false greens, and CI provisions the real floor (t39)

t38 found two holes in the drift gate itself.

F2 — the job could never run where it mattered. Home Assistant 2026.10.1
declares ``Requires-Python >=3.14.2`` (PyPI metadata), so the old guard let a
3.13 runner through and the ``homeassistant>=2026.10`` install then failed with
a resolver error. The job now provisions its own interpreter
(``actions/setup-python@v5`` with ``python-version: "3.14"``) and the guard runs
against the REAL floor, read from ``ha_api_drift.HOMEASSISTANT_PYTHON_FLOOR`` —
one source of truth, pinned by a test against the installed distribution's own
``Requires-Python`` metadata. Verified: on 3.13.16 the guard refuses with
"Home Assistant needs Python >= 3.14.2, but this job runs 3.13.16 / Fix: raise
actions/setup-python…"; on 3.14.8 it reports "interpreter ok"; and
``uvx --python 3.14 --with 'homeassistant>=2026.10'`` resolves 2026.10.1.

F1 — the standalone entry point was a false green. It printed counters and
exited 0 even when it had walked nothing, which is exactly how the manual
red-proof tool gets misused. The non-vacuity floors now live in
``ha_api_drift.FLOORS`` and are enforced in ONE place, ``Report.floor_violations()``,
used by the pytest wrapper and by ``__main__`` (so the constants cannot drift
apart; a test asserts the wrapper holds no floor-like constants of its own).
On top of that the sweep can no longer lie in either direction:

* an empty or mis-targeted directory reports ``FLOOR:`` lines and
  ``drift sweep FAILED`` and exits 1 (a non-existent path is a ``bad-path``
  finding, not a traceback and not a silent zero-module sweep);
* with no homeassistant installed it returns a single ``no-homeassistant``
  finding with zero counters — never a wall of phantom "broken-import"s, never
  a green exit.

Verified in the CI-equivalent environment (Python 3.14.8 + homeassistant
2026.10.1): HEAD exits 0 with "no Home-Assistant API drift (13 modules, 60
imports, 35 call arguments, 7 awaited HA calls)"; the empty directory exits 1
with 4 FLOOR lines and no findings; a missing path exits 1 with the ``bad-path``
finding; and the full pre-fix tree (``git archive 5ede4fe``) exits 1 with
exactly the three t36 drifts (media_player.py:965 BrowseMediaSource,
diagnostics.py:93 homeassistant.util.diagnostic, config_flow.py:425
missing-await) and 0 floor violations.

The fast ``test`` job and ``release.yml`` are untouched; the workflow is
unchanged in shape except the new provisioning + guard steps, and parses as
valid YAML.

tests/test_ha_api_drift.py

@@ -11,6 +11,9 @@ The sweep itself lives in ``tests/ha_api_drift.py`` (documented there).
 
 from __future__ import annotations
 
+import ast
+import subprocess
+import sys
 from pathlib import Path
 
 import ha_api_drift
@@ -77,13 +80,12 @@ def test_the_sweep_is_not_vacuous():
 
     report = ha_api_drift.scan()
 
-    # Floors, not targets: they sit below today's walk (13 modules, 60 imports,
-    # 35 checked arguments, 7 awaited HA calls) so a broken walker shows up as a
-    # failure instead of a silently green sweep.
-    assert report.modules >= 10, report
-    assert report.imports >= 40, report
-    assert report.call_args >= 20, report
-    assert report.awaited_calls >= 5, report
+    # Floors, not targets: the numbers live in ha_api_drift.FLOORS — one source
+    # of truth for this wrapper and the standalone entry point (t39 F1) — so a
+    # broken or mis-targeted walk fails here instead of looking green.
+    violations = report.floor_violations()
+
+    assert violations == [], "\n".join(violations)
 
 
 def test_the_sweep_flags_the_pre_fix_defects(tmp_path):
@@ -128,3 +130,79 @@ def test_the_sweep_accepts_the_fixed_forms(tmp_path):
     report = ha_api_drift.scan(tmp_path)
 
     assert report.findings == [], "\n" + str(report)
+
+
+def _run_drift_module(*paths):
+    """Run the standalone entry point in this (HA-bearing) interpreter."""
+    return subprocess.run(
+        [
+            sys.executable,
+            str(Path(ha_api_drift.__file__).resolve()),
+            *[str(path) for path in paths],
+        ],
+        capture_output=True,
+        text=True,
+        check=False,
+    )
+
+
+def test_the_standalone_entry_point_passes_on_the_production_tree():
+    """F1: the CLI is the sweep, with the same verdict on the real tree."""
+    result = _run_drift_module()
+
+    assert result.returncode == 0, result.stderr
+    assert "no Home-Assistant API drift" in result.stdout
+
+
+def test_the_standalone_entry_point_fails_on_an_empty_directory(tmp_path):
+    """t39 F1: zeros must not exit 0 — the floors apply to the CLI too."""
+    result = _run_drift_module(tmp_path)
+
+    assert result.returncode != 0
+    assert "0 modules" in result.stdout  # the counter that used to look green
+    assert "FLOOR:" in result.stderr
+    assert "drift sweep FAILED" in result.stderr
+
+
+def test_the_standalone_entry_point_fails_on_a_missing_path(tmp_path):
+    """A mis-specified path is a failure, not a silent zero-module sweep."""
+    result = _run_drift_module(tmp_path / "not-a-directory")
+
+    assert result.returncode != 0
+    assert "bad-path" in result.stdout
+
+
+def test_no_floor_constants_are_duplicated_in_this_wrapper():
+    """F1: the floors come from ha_api_drift.FLOORS — nowhere else."""
+    source = Path(__file__).read_text(encoding="utf-8")
+    tree = ast.parse(source)
+
+    local_ints = [
+        target.id
+        for node in tree.body
+        if isinstance(node, ast.Assign)
+        for target in node.targets
+        if isinstance(target, ast.Name)
+        and isinstance(node.value, ast.Constant)
+        and isinstance(node.value.value, int)
+    ]
+
+    assert local_ints == [], f"floor-like constants belong in ha_api_drift: {local_ints}"
+    assert "floor_violations" in source
+
+
+def test_the_declared_python_floor_never_lags_homeassistant():
+    """F2: the CI guard's floor is HA's own Requires-Python, not a guess."""
+    _require_installed_homeassistant()
+
+    import importlib.metadata as metadata
+
+    declared = metadata.metadata("homeassistant")["Requires-Python"]
+    parsed = ha_api_drift.parse_requires_python(declared)
+
+    assert parsed is not None, f"unparsable Requires-Python: {declared!r}"
+    assert tuple(parsed) <= ha_api_drift.HOMEASSISTANT_PYTHON_FLOOR, (
+        f"tests/ha_api_drift.py declares {ha_api_drift.HOMEASSISTANT_PYTHON_FLOOR} "
+        f"but the installed homeassistant requires {declared} — raise the constant "
+        f"and the setup-python version in .gitea/workflows/test.yml"
+    )