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/plugins/homeassistant/test_service.py

@@ -111,9 +111,10 @@ def test_the_overview_names_what_needs_a_look_and_no_more():
 
 def test_system_problems_are_read_from_what_home_assistant_answers():
     healthy = s.read_health({"config": {"recovery_mode": False}, "issues": [], "resolution": {"unhealthy": [], "unsupported": []},
-                             "host": {"disk_free": 99.8, "disk_total": 116.5}, "addons": [{"slug": "a", "state": "started"}]})
+                             "host": {"disk_free": 99.8, "disk_used": 12.0, "disk_total": 116.5},
+                             "addons": [{"slug": "a", "state": "started"}]})
     assert healthy["problems"] == [] and healthy["repairs_read"] and healthy["supervised"]
-    assert healthy["disk_free_pct"] == 85.7
+    assert healthy["disk_free_pct"] == 85.7 and healthy["disk_used_gb"] == 12.0 and healthy["disk_used_pct"] == 10.3
     bad = s.read_health({
         "config": {"recovery_mode": True},
         "issues": [{"domain": "hassio", "translation_key": "issue_system_reboot_required", "severity": "warning"},
@@ -133,7 +134,8 @@ def test_system_problems_are_read_from_what_home_assistant_answers():
 
 def test_what_home_assistant_wouldnt_answer_is_not_read_as_fine():
     found = s.read_health({"config": {}, "issues": None, "resolution": None, "host": None, "addons": None})
-    assert not found["repairs_read"] and not found["supervised"] and found["disk_free_pct"] is None
+    assert not found["repairs_read"] and not found["supervised"]
+    assert found["disk_free_pct"] is None and found["disk_used_pct"] is None
 
 
 def test_a_schedule_installs_add_ons_then_core_then_the_os():