Screen: switch off by itself when nothing is going on

With `general.screen.off_command` set, the monitor switches off once nothing has
played and nobody has done anything for `auto_off_minutes` (15 by default, 0 for
never, editable in parent mode). "Doing anything" is any intent a person could
have caused: a remote key, a web command, or a key press or tap in the kiosk,
which the page reports at most every 30s via POST /api/screen/activity. The first
such intent after an auto-off runs `on_command`, so the remote wakes the screen
too. The auto-off itself is silent; switches a person asks for still blubb.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

python-backend/tests/test_settings.py

@@ -8,7 +8,7 @@ from pathlib import Path
 import httpx2
 import pytest
 
-from musicmouse.config import WebConfig, load_config
+from musicmouse.config import ScreenConfig, WebConfig, load_config
 from musicmouse.services.web.service import build_app
 from musicmouse.services.web.settings import to_device_volume, to_percent
 from musicmouse.simulator.harness import Simulation, build_simulation
@@ -99,8 +99,46 @@ def test_a_degenerate_range_reads_as_full(config_dir: Path) -> None:
 
 async def test_settings_expose_only_the_editable_subset(client: httpx2.AsyncClient) -> None:
     body = (await client.get("/api/settings")).json()
-    assert set(body) == set(SETTINGS)
+    assert set(body) == {*SETTINGS, "screen_auto_off_minutes"}
     assert body["max_volume"] == 60
+    assert body["screen_auto_off_minutes"] is None  # no screen to switch off
+
+
+async def test_the_screen_auto_off_is_read_and_saved_into_its_section(
+    client: httpx2.AsyncClient, sim: Simulation, config_dir: Path
+) -> None:
+    path = config_dir / "config.yml"
+    path.write_text(
+        COMMENTED.replace(
+            "\nfigures:",
+            "  screen:\n    toggle_command: kiosk-screen toggle\n"
+            "    off_command: kiosk-screen off\n\nfigures:",
+        ),
+        encoding="utf-8",
+    )
+    sim.app.config.general.screen = ScreenConfig(
+        toggle_command="kiosk-screen toggle", off_command="kiosk-screen off"
+    )
+    assert (await client.get("/api/settings")).json()["screen_auto_off_minutes"] == 15
+
+    response = await client.put("/api/settings", json={**SETTINGS, "screen_auto_off_minutes": 30})
+    assert response.status_code == 200
+    assert response.json()["screen_auto_off_minutes"] == 30
+    assert sim.app.config.general.screen.auto_off_minutes == 30  # live, for ScreenService
+
+    reloaded = load_config(path)
+    assert reloaded.general.screen is not None
+    assert reloaded.general.screen.auto_off_minutes == 30
+    assert "screen_auto_off_minutes" not in path.read_text(encoding="utf-8")
+
+
+async def test_the_screen_auto_off_without_a_screen_is_ignored(
+    client: httpx2.AsyncClient, config_dir: Path
+) -> None:
+    response = await client.put("/api/settings", json={**SETTINGS, "screen_auto_off_minutes": 30})
+    assert response.status_code == 200
+    assert response.json()["screen_auto_off_minutes"] is None
+    assert "screen" not in (config_dir / "config.yml").read_text(encoding="utf-8")
 
 
 # -------------------------------------------------------------------------- writing