Allow partial SONOFF water valve composite settings

[MaxRink]

Summary

• merge partial writes for SONOFF SWV-ZFE seasonal watering adjustment settings
• merge partial writes for valve alarm settings
• merge irrigation plan updates with the current settings or latest plan report before encoding the payload
• expand tests to cover manual defaults, seasonal adjustment, valve alarm, and irrigation plan partial updates

Testing

• npx pnpm@10.12.1 run check
• npx pnpm@10.12.1 vitest run test/sonoff.test.ts --config ./test/vitest.config.mts
• npx pnpm@10.12.1 vitest run test/shelly.test.ts test/sonoff.test.ts --config ./test/vitest.config.mts

[MaxRink]

Validated against a local Docker Home Assistant + MQTT discovery harness. The screenshot shows the rendered HA UI for the composite child entities, Shelly cover lift-only vs slat-capable cover, and SONOFF valve controls.

[Koenkk]

thanks!