Leave out unusable rooms instead of pausing; add keep-last-value option

A single stale, unavailable, missing or invalid room sensor paused
learning and forecasts for every room. That is not acceptable once the
MPC may control heating.

Now such a room is left out: the weighted temperature, learning and the
optimizer use the remaining rooms with their weights re-normalized, and
a room learns only across poll pairs where it was usable at both ends.
Readiness considers only the rooms used. Everything pauses only when no
room is usable or a shared input (relay, thermostat, outdoor
temperature) is missing.

A new setup/Configure checkbox, room_stale_use_last_value (default off),
keeps using a stale room sensor's last value instead, for sensors that
report only on change. It never applies to unavailable or invalid
sensors, or to a sensor silent for more than 24 hours.

Status adds excluded_rooms, weight_coverage and a per-room "used" flag.
English and Romanian labels and help text added.

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

tests/ha/test_config_flow.py

@@ -15,6 +15,7 @@ async def test_config_flow(hass, inputs):
     validated = result["data_schema"](main)
     assert validated["room_max_age_minutes"] == 30
     assert validated["weather_max_age_minutes"] == 120
+    assert validated["room_stale_use_last_value"] is False
     result = await hass.config_entries.flow.async_configure(result["flow_id"], validated)
     assert result["step_id"] == "weather"
     result = await hass.config_entries.flow.async_configure(
@@ -35,7 +36,7 @@ async def test_options_flow_keeps_settings(hass, entry, inputs):
     result = await hass.config_entries.options.async_init(entry.entry_id)
     main = result["data_schema"]({"climate_entity": "climate.reference",
                                  "heater_entity": "switch.boiler", "room_entities": ["sensor.room"],
-                                 "room_max_age_minutes": 45})
+                                 "room_max_age_minutes": 45, "room_stale_use_last_value": True})
     result = await hass.config_entries.options.async_configure(result["flow_id"], main)
     result = await hass.config_entries.options.async_configure(
         result["flow_id"], result["data_schema"]({"outside_temperature_sources": ["sensor.outside"]}))
@@ -44,7 +45,14 @@ async def test_options_flow_keeps_settings(hass, entry, inputs):
     assert result["type"] is FlowResultType.CREATE_ENTRY
     await hass.async_block_till_done()
     assert entry.options["room_max_age_minutes"] == 45
-    assert hass.data[DOMAIN][entry.entry_id].config["room_max_age_minutes"] == 45
+    coordinator = hass.data[DOMAIN][entry.entry_id]
+    assert coordinator.config["room_max_age_minutes"] == 45
+    assert coordinator.config["room_stale_use_last_value"] is True
+    # The next options form shows the saved choice.
+    result = await hass.config_entries.options.async_init(entry.entry_id)
+    assert result["data_schema"]({"climate_entity": "climate.reference", "heater_entity": "switch.boiler",
+                                  "room_entities": ["sensor.room"]})["room_stale_use_last_value"] is True
+    hass.config_entries.options.async_abort(result["flow_id"])
 
 
 async def test_v1_entry_migrates_on_setup(hass, inputs):