Native Statistics Support for climate Entities

[techno-Dev-81]

Describe your core improvement

Enable native statistics tracking for climate entities by exposing key numeric attributes (e.g. current_temperature, temperature) as internal sensor entities with proper metadata (state_class, device_class, unit_of_measurement).
This would allow long-term analytics, energy dashboard integration, and historical graphing without requiring duplicate template sensors.

Current limitations

Home Assistant does not support state_class on climate entities, making them ineligible for inclusion in the statistics engine.
Users must manually create wrapper sensor entities to extract values like current_temperature, which introduces duplication, clutter, and maintenance overhead.
These workarounds are fragile and break modularity—especially in production-grade setups.

Technical benefits

• Eliminates redundant template sensors and reduces entity bloat
• Enables direct integration with energy dashboards and analytics
• Improves UI consistency by allowing inline historical graphs on climate cards
• Enhances auditability and rollback safety by removing workaround dependencies
• Aligns with Home Assistant’s declarative, metadata-driven architecture

Additional context

This limitation disproportionately affects users with structured, self-hosted stacks (e.g. Zigbee2MQTT) where MQTT discovery auto-generates entities without state_class. Since these attributes cannot be injected post-discovery or via UI, users are forced to duplicate logic just to expose already-available values. This breaks modular design principles and increases upgrade risk. A native solution would restore architectural integrity and reduce friction for advanced users.