P2-1: Guard SessionId NPE with safe-call in SessionsReducer
P2-2: Remove 16 dead event classes + reducer branches; replace with live orchestration events in tests
P2-3: Standardize ChatInput divergences — guard CancelSession, single-arg ProtocolError
P2-4: Remove dead TuiToolRecord.diff and ToolDisplayStatus.REQUESTED
P2-5: Remove dead streamLive from SessionEventBridge
P2-6: Extract SessionsReducerContext data class for 6+ param method
P2-7: Replace StageId("none") sentinel with TypeId.NONE
P2-9: Add TypeId.random() factory on all type-alias IDs
P2-10: Add KDoc on schemaVersion documenting reserved-for-migration
P2-8: Verified RouterReducer string-template already correct (TypeId value class toString)
kami
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