Add charging mode select to Silla Prism

[ebaschiera]

Breaking change

Proposed change

The initial Silla Prism PR (#176785) was reduced to a single platform for review, with the controls left as follow-ups. This is the first of them: the charging mode select.

The Prism publishes the port operating mode on a retained topic and accepts a set_mode command on the matching command topic, so the select reads its state from the accumulated status and writes back through the library's command builders. To make that possible, the coordinator now passes a publish callback to PrismDevice, mapping it onto mqtt.async_publish. That callback is the plumbing every remaining control platform will reuse.

Only Solar, Normal and Pause are user-settable. The Prism also reports a fourth mode when its own load balancing suspends the session; it cannot be selected back, so current_option returns None and the entity reads as unknown while it lasts. The port state remains visible on the status sensor throughout.

The shared test helper gained an optional platform list, since snapshot_platform requires a single loaded platform and the integration now sets up two.

No library change is needed: pysillaprism 0.2.0 already exposes the command surface.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue: Add Silla Prism integration #176785
• Link to documentation pull request: Document the Silla Prism charging mode select home-assistant.io#47928
• Link to developer documentation pull request:
• Link to frontend pull request:

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