fix(diarization): учтён системный power profile

Зачем:
- часть Intel-стендов не публикует ACPI platform_profile
- balanced-режим на таком стенде доступен через power-profiles-daemon

Что:
- добавлен fallback на powerprofilesctl get
- поведение закреплено тестом

Проверка:
- uv run pytest -q tests/test_benchmark_experiment.py
- uv run ruff check для изменённых файлов

src/local_transcriber/benchmark_experiment.py

@@ -931,6 +931,24 @@ def _runtime_supply() -> str | None:
     return None
 
 
+def _runtime_profile() -> str | None:
+    profile = _read_optional_text(Path("/sys/firmware/acpi/platform_profile"))
+    if profile is not None:
+        return profile
+    try:
+        completed = subprocess.run(
+            ["powerprofilesctl", "get"],
+            capture_output=True,
+            text=True,
+            check=False,
+            timeout=5,
+        )
+    except (OSError, subprocess.TimeoutExpired):
+        return None
+    value = completed.stdout.strip()
+    return value or None if completed.returncode == 0 else None
+
+
 def _runtime_governor() -> str | None:
     values = {
         value
@@ -1006,7 +1024,7 @@ def runtime_guard_snapshot() -> dict[str, Any]:
     swap = psutil.swap_memory()
     return {
         "supply": _runtime_supply(),
-        "profile": _read_optional_text(Path("/sys/firmware/acpi/platform_profile")),
+        "profile": _runtime_profile(),
         "governor": _runtime_governor(),
         "turbo": _runtime_turbo(),
         "power_limits": _runtime_power_limits(),

tests/test_benchmark_experiment.py

@@ -593,6 +593,19 @@ def test_schedule_preserves_raw_repeats_and_resumes_only_success(tmp_path):
     assert all(item["guard"]["attempts"][0]["valid"] for item in second["cells"])
 
 
+def test_runtime_profile_falls_back_to_powerprofilesctl(monkeypatch):
+    monkeypatch.setattr(experiment, "_read_optional_text", lambda _path: None)
+    monkeypatch.setattr(
+        experiment.subprocess,
+        "run",
+        lambda *args, **kwargs: experiment.subprocess.CompletedProcess(
+            args[0], 0, stdout="balanced\n", stderr=""
+        ),
+    )
+
+    assert experiment._runtime_profile() == "balanced"
+
+
 def test_runtime_guard_retries_once_and_persists_transition_evidence(tmp_path):
     manifest = _manifest(tmp_path)
     manifest["cells"][1]["enabled"] = False