Reset ViewStore state when store changes

[hkusu]

Summary

• recreate the Compose state holder when rememberViewStore adopts a different Store
• add a regression test that verifies the first composition after a key change reads the new Store state

Why

• keep state identity aligned with dispatch and event bindings on a per-Store basis
• avoid carrying state across Store switches

Testing

• JAVA_HOME=/Users/h_kusu/Library/Java/JavaVirtualMachines/AndroidStudio/Contents/Home ./gradlew :koma-compose:jvmTest