refactor(agent): remove message metadata channel

packages/client/runtime/src/client/sessions/conversation.ts

@@ -74,7 +74,6 @@ export interface ContextMessageNode {
   seq: number
   content: readonly ContentBlock[]
   source: unknown
-  meta?: unknown
 }
 
 /** A tool result paired (when in-window) with its call head. */

packages/client/runtime/src/client/sessions/fold-adapter.ts

@@ -43,7 +43,6 @@ function materializeNode(
       if (event.data.source.kind !== 'user') {
         return {
           kind: 'context', seq: event.seq, content: event.data.content, source: event.data.source,
-          meta: event.data.meta,
         }
       }
       return { kind: 'user', seq: event.seq, content: event.data.content, source: event.data.source }