Miele - fix core temperature reading

[aturri]

Proposed change

Add guards and fix mappings of invalid temperatures, as some appliances use "-3276800" as invalid value (in addition to "-32768"), in order to correctly show the "unknown" state on temperature sensors.

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 #
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[home-assistant]

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

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[Copilot]

Pull request overview

This PR fixes invalid temperature value handling in the Miele integration by adding guards to prevent displaying invalid API sentinel values as actual temperature readings. The integration now correctly handles both "-32768" (used by most devices) and "-3276800" (used by some devices) as "no reading" sentinels, ensuring temperature sensors show "unknown" state when the probe is inactive rather than displaying bogus numeric temperatures.

Changes:

• Enhanced _convert_temperature() function with proper None checks and exception handling for Type/Value errors
• Extended DISABLED_TEMP_ENTITIES tuple to include scaled sentinel values (-32768.0 and -32766.0) for devices that report int16 minimum values already in degrees
• Added STEAM_OVEN_MK2 appliance type support to the core temperature sensor definition
• Improved comments to clarify the logic for optional temperature datapoints
• Added two comprehensive test cases covering both sentinel value scenarios

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
homeassistant/components/miele/sensor.py	Enhanced temperature conversion with error handling and added STEAM_OVEN_MK2 support for core temperature sensors
homeassistant/components/miele/const.py	Extended DISABLED_TEMP_ENTITIES with scaled sentinel values and added clarifying comments
tests/components/miele/test_sensor.py	Fixed comment typo and added two new test functions to verify unknown state handling for both sentinel values