[Feature request]: Expose 'actual_irrigation_amount' as a standalone sensor for Sonoff SWV / Zigbee Smart Water Valve

Is your feature request related to a problem? Please describe

I am using the Sonoff SWV (SWV-ZFE) Zigbee Smart Water Valve in Home Assistant via Zigbee2MQTT. Currently, the real-time water consumption for the active irrigation cycle is nested inside the JSON string payload of irrigation_schedule_status under the key actual_irrigation_amount.

Because Home Assistant has a strict 255-character limit for entity states, long JSON strings pushed directly as state values get truncated.

Furthermore, the currently exposed x_real_time_irrigation_volume sensor is misleadingly named: it behaves as a daily total volume (resets at midnight and updates every 5 minutes) rather than showing the actual real-time volume of the ongoing cycle.

Describe the solution you'd like

It would be great if Zigbee2MQTT could expose actual_irrigation_amount directly as a standalone sensor (e.g. sensor.<device>_actual_irrigation_amount with unit L).

Having this as a dedicated sensor would:

• Avoid truncation issues caused by the HA 255-character state limit;
• Allow users to easily track exact real-time water consumption during each irrigation run and use it natively in Home Assistant dashboards or automations.

Describe alternatives you've considered

Currently using string-splitting workaround templates in Home Assistant to extract 'actual_irrigation_amount' from the truncated irrigation_schedule_status state, which is fragile and inefficient.

If anyone needs to extract the real-time value from the truncated state (e.g., using custom:template-entity-row or a template sensor), you can use this extraction logic:

{% set value = states('sensor.irrigazione_giardino_irrigation_schedule_status') %}
{% if 'actual_irrigation_amount' in value %}
  {{ value.split("'actual_irrigation_amount': ")[1].split(',')[0] | trim }} L
{% else %}
  N/D
{% endif %}

Additional context

Device information

• Device Model: SONOFF SWV / SWV-ZFE (Zigbee Smart Water Valve)
• Integration: Zigbee2MQTT

Start by locating the Sonoff SWV/SWV-ZFE device converter and the existing irrigation_schedule_status and x_real_time_irrigation_volume definitions. Expose actual_irrigation_amount as a standalone sensor with unit L, then add or update the relevant converter tests to verify the value and naming.