refactor(agent-loop): separate injected context from turns

packages/core/session/tests/session.spec.ts

@@ -2,7 +2,6 @@ import { describe, expect, expectTypeOf, it, vi } from 'vitest'
 import { Context } from 'cordis'
 import { CallId } from '@deepseek-ai/dsh-llm'
 import SessionStore, {
-  displayPromptContent,
   findLastMessageTurnEnd,
   SESSION_FORMAT_VERSION,
   Session,
@@ -136,35 +135,6 @@ describe('Session', () => {
     expect(steeringMessage!.content).toEqual([{ type: 'text', text: 'focus on tests' }])
   })
 
-  it('derives baked prompt context while exposing only the direct prompt for display', () => {
-    const session = new Session(SessionId('prompt-envelope'))
-    const event = session.append('user/message', {
-      content: [
-        { type: 'text', text: 'background' },
-        { type: 'text', text: '\n\n## My request:\n' },
-        { type: 'text', text: 'question' },
-      ],
-      source: { kind: 'user' },
-      envelope: {
-        displayContent: [{ type: 'text', text: 'question' }],
-        prefixContexts: [{ source: { kind: 'plugin', plugin: 'reference' } }],
-      },
-    }, { surfaceOp: 'append' })
-
-    expect(session.deriveMessages()).toEqual([{
-      role: 'user',
-      content: [
-        { type: 'text', text: 'background' },
-        { type: 'text', text: '\n\n## My request:\n' },
-        { type: 'text', text: 'question' },
-      ],
-    }])
-    expect(displayPromptContent(event.data)).toEqual([{ type: 'text', text: 'question' }])
-    expect(Object.isFrozen(event.data.envelope?.displayContent)).toBe(true)
-    expect(new Session(SessionId('prompt-envelope-replay'), session.events).deriveMessages())
-      .toEqual(session.deriveMessages())
-  })
-
   it('keeps context source durable in the event while hiding it from the projection', () => {
     const session = new Session(SessionId('s2-raw'))
     session.append('user/message', {