Deduplicate ConversationStateUpdateEvent definition

Problem

ConversationStateUpdateEvent is defined in two places with different shapes:

src/events/types.ts (line ~133):

export interface ConversationStateUpdateEvent extends BaseEvent {
  kind: 'ConversationStateUpdateEvent';
  key: string;
  value: unknown;
  previous_value?: unknown;  // has this field
}

src/conversation/remote-state.ts (line ~18):

export interface ConversationStateUpdateEvent extends Event {
  kind: 'ConversationStateUpdateEvent';
  key: string;
  value: any;  // uses any instead of unknown
  // missing previous_value
}

Different base types (BaseEvent vs Event), different value types (unknown vs any), and the remote-state version is missing previous_value.

Proposed Fix

• Delete the definition in remote-state.ts
• Import from events/types.ts instead
• This is a one-line import change

Impact

Low — small cleanup but eliminates a source of confusion.

This issue was created by an AI agent (OpenHands) on behalf of Robert Brennan.

Start by comparing the ConversationStateUpdateEvent definitions in src/events/types.ts around line 133 and src/conversation/remote-state.ts around line 18. Replace the remote-state definition with the import from events/types.ts, then verify that only one definition remains and the remote-state usage accepts previous_value and unknown values.