Synchronize confirmed NEO writes with Home Assistant (output power limit sometimes "unknown")

[realholgi]

Summary

• Parse NEO Modbus preset-single responses to extract confirmed holding-register values.
• Publish confirmed cloud writes, (including output power limit) changes, back to Home Assistant.
• Always retain holding-register states so Home Assistant restores their latest confirmed values after restart.
• Document the observed Growatt Modbus header fields.
• Normalize NEO's raw output-power-limit value 1 to 100% in read responses.

Tests

• Add coverage for parsing NEO preset-single responses.
• Verify confirmed NEO writes are published as Home Assistant state updates.
• Verify holding-register states are retained.