Google Cast: detect state and attributes when device is doing active non-media casting

[nopoz]

Proposed change

This PR fixes an issue where Cast devices running custom receiver applications (such as DashCast) are incorrectly reported as off in Home Assistant.

Currently, the integration checks self._chromecast.is_idle before checking if a specific app_id is active. Many custom apps do not implement the media namespace or report status in a way pychromecast expects, resulting in the library reporting the device as idle/standby even when the app is visible on screen.

This change reorders the checks in the state property. It now checks for a valid app_id before checking the idle status.

• If a valid app_id is present (and it is not the default APP_BACKDROP), the state is reported as IDLE (or PLAYING for known unreliable apps).
• This ensures the entity remains available in Home Assistant, allowing users to see the app_id attribute or stop the application.
• The default screensaver (Backdrop) continues to correctly report as OFF.

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 Google Cast Integration does not populate state for custom receiver applications #160814
• This PR is related to issue: Google Cast Integration does not populate state for custom receiver applications #160814
• Link to documentation pull request:
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

• I understand the code I am submitting and can explain how it works.
• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.
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• Documentation added/updated for www.home-assistant.io

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  Updated and included derived files by running: python3 -m script.hassfest.
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[home-assistant]

Hey there @emontnemery, mind taking a look at this pull request as it has been labeled with an integration (cast) you are listed as a code owner for? Thanks!

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