[Feature Request] Expose ViewModel Change event

Submission checklist

• I have confirmed the issue is present in the latest version of the Rive Unity package
• I have searched the documentation and forums and could not find an answer
• I have searched existing issues and this is not a duplicate

Description

To reduce errors, our project has created strongly typed wrappers around the Rive view models in the game. However a common issue we face is that game logic can bind a new instance of a view model, leading to stale references to view models.

This isn't generally a problem when simply retrieving or setting values as our wrappers reobtain the root view model instances from the state machine each time, however we haven't found a good solution to ensuring that events such as OnTrigger and OnChange are always subscribed to the latest version of a property.

Previous working version

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Reproduction steps / code

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Upload your reproduction files / stack trace

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Source .riv / .rev file

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Screenshots / video

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Unity Editor log file

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Rive Unity package version

v0.4.5

Unity version

v6000.5.0f1

Target platform

macOS

Editor OS & version

macOS Tahoe 26.5.2

Additional context

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No file, test, or entry point is named. Start by tracing how Unity ViewModel instances are rebound and how existing OnTrigger and OnChange subscriptions are exposed; define the required change event behavior and verify that subscribers receive updates for the latest bound ViewModel instance.