docs: keep compare_tariff sensors in the FAQ recorder example

docs/compare.md

@@ -142,6 +142,10 @@ For each tariff a new sensor is created in Home Assistant called **predbat.compa
 
 You can create charts from these sensors to show how the different tariffs compare on a daily basis.
 
+The day-by-day history on the Compare tab is read back from Home Assistant's recorded history of these sensors, so they must be kept by the recorder.
+If you have added a `recorder:` filter that excludes the `predbat` domain, include them again with an `entity_globs` entry of `predbat.compare_tariff_*`
+(see the [recorder example in the FAQ](faq.md#predbat-is-causing-exceed-maximum-size-warning-messages-in-the-home-assistant-core-log)), otherwise the Compare tab will only ever show the most recent run.
+
 ![image](https://github.com/user-attachments/assets/6d5c30f6-822f-4d9c-b4a6-701c0b676c61)
 
 ## Overriding Predbat configuration per tariff

docs/faq.md

@@ -252,6 +252,8 @@ recorder:
       - sensor.predbat_pv_d3
       - sensor.predbat_temperature
   include:
+    entity_globs: #The history of these entities is used by Predbat's Compare tab
+      - predbat.compare_tariff_*
     entities: #The history of these entities is used by Predbat
       - predbat.car_charging_power
       - predbat.carbon_today
@@ -289,7 +291,8 @@ Two things to be careful of if you adapt the example above:
 
 - Don't drop entries from the `include` list without checking what reads them. Predbat needs the recorded history of
 every entity listed there and quietly loses a feature for each one it can no longer read - `predbat.cost_today`, for
-instance, is what the Plan tab's *History* and *Yesterday Without Predbat* views are built from.
+instance, is what the Plan tab's *History* and *Yesterday Without Predbat* views are built from. Likewise the `predbat.compare_tariff_*`
+sensors are what the [Compare tab](compare.md) builds its day-by-day history from; without them it only ever shows the latest run.
 - Don't add further Predbat sensors to the `exclude` list for the same reason. `sensor.predbat_pv_forecast_h0`,
 `sensor.predbat_pv_forecast_h0_uncalibrated` and `sensor.predbat_pv_today` are deliberately left out of it because PV
 calibration, the PV chart and the PV accuracy chart compare against their history. Adding a `sensor.*` entity to