fix(homeassistant): storage reads used of total with its percentage, and an OS update is said to wait on a reboot (#6753, #6754)

The tile shows Home Assistant's own used figure beside the total, so it matches
Home Assistant's storage page. An OS update doesn't reboot the machine: Supervisor
writes the image, reports the new version and raises a repair asking for a reboot.
The confirmation, schedule warning, MCP docs and plugin docs now say so.

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

tests/integration/test_homeassistant.py

@@ -533,18 +533,29 @@ def test_a_poll_keeps_the_system_problems_and_records_them(app):
     assert metrics["problems_open"] == 2.0 and metrics["disk_free_pct"] == 50.0 and metrics["update_failed"] == 0.0
 
 
-def test_the_page_shows_the_devices_storage_and_how_full_it_is(app):
+def test_the_page_shows_storage_used_of_the_total_with_the_percentage(app):
     async def go():
-        await _clean(app, health={"repairs_read": True, "problems": [], "disk_free_gb": 99.8,
-                                  "disk_total_gb": 116.5, "disk_free_pct": 85.7})
+        await _clean(app, health={"repairs_read": True, "problems": [], "disk_free_gb": 99.8, "disk_used_gb": 12.0,
+                                  "disk_total_gb": 116.5, "disk_free_pct": 85.7, "disk_used_pct": 10.3})
         web, _ = await _admin_client(app)
         return await (await web.get("/plugins/homeassistant/")).get_data(as_text=True)
 
     page = asyncio.run(go())
-    assert "116.5 GB" in page and "14% full" in page
+    assert "12.0 of 116.5 GB (10%)" in page
     assert "Disk free" not in page
 
 
+def test_the_page_says_an_os_update_waits_on_a_reboot_rather_than_making_one(app):
+    async def go():
+        await _clean(app)
+        web, _ = await _admin_client(app)
+        return await (await web.get("/plugins/homeassistant/")).get_data(as_text=True)
+
+    page = asyncio.run(go())
+    assert "takes effect only once you reboot the machine" in page
+    assert "reboots the machine" not in page
+
+
 def test_a_report_it_couldnt_read_leaves_the_last_one_and_home_assistant_still_answers(app):
     sched = _ha("scheduler")
     ha = FakeHomeAssistant()