fix(storage): defer binding updates until ensemble.storage.clear() completes

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Description

Fixes a race in EnsembleStorage.clear(): StorageManager.clearPublicStorage() is asynchronous (each GetStorage.remove is awaited in a loop), but storage binding listeners handle ModelChangeEvent by re-evaluating the full binding expression via dataContext.eval(), which reads the current value from GetStorage. Firing those dispatches immediately after starting the async clear meant listeners could still read non-null persisted values and repopulate bound widgets, so the UI could appear uncleared until an unrelated rebuild.

Related Issue

None filed; same root cause as the investigation in #2227 (that PR was closed with no code landed).

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)

What Has Changed

• EnsembleStorage.clear() now uses unawaited(StorageManager().clearPublicStorage().whenComplete(...)) so ScreenController.dispatchStorageChanges runs only after the async clear finishes (or fails), preserving the synchronous invokable surface for scripts while fixing ordering for bindings.

How to Test

1. From modules/ensemble, run flutter test (including test/ensemble_storage_clear_test.dart and test/storage_manager_test.dart).
2. Manually: bind a widget property to \${ensemble.storage.someKey}, call ensemble.storage.clear() from an action, and confirm the bound UI reflects cleared storage without needing a second interaction or navigation.

Screenshots / Videos

N/A

Checklist

• I have run flutter analyze and addressed any new warnings
• I have run flutter test and all tests pass
• I have tested my changes on the relevant platform(s)
• I have updated documentation if needed
• My changes do not introduce new warnings or errors

Note: The CI/automation image used here did not have the Flutter SDK on PATH, so flutter analyze / flutter test were not executed in this environment. Please run them locally per AGENTS.md.