refactor(agent-loop): simplify message machine

packages/acp/acp/src/codec.ts

@@ -18,7 +18,6 @@ export function turnEndToStopReason(reason: TurnEndReason): StopReason {
     case 'max-tokens':
       return 'max_tokens'
     case 'aborted':
-    case 'disposed':
     case 'interrupted':
       return 'cancelled'
     case 'error':

packages/acp/acp/tests/approval.spec.ts

@@ -20,7 +20,7 @@ describe('ACP machine permission policy', () => {
     await harness.client.initialize({ protocolVersion: PROTOCOL_VERSION, clientCapabilities: {} })
     const { sessionId } = await harness.client.newSession({ cwd: process.cwd(), mcpServers: [] })
     const agent = harness.ctx.agents.get(SessionId(sessionId))!
-    agent.session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    agent.session.append('turn/start', { turn: 1 })
     return { agent, toolName: 'bash', callId: CallId('call-9'), ...overrides }
   }
 

packages/acp/acp/tests/codec.spec.ts

@@ -7,10 +7,9 @@ describe('ACP automation codec', () => {
     const cases: [TurnEndReason, string][] = [
       [{ kind: 'completed' }, 'end_turn'],
       [{ kind: 'max-tokens' }, 'max_tokens'],
-      [{ kind: 'aborted' }, 'cancelled'],
-      [{ kind: 'disposed' }, 'cancelled'],
+      [{ kind: 'aborted', reason: { kind: 'user' } }, 'cancelled'],
       [{ kind: 'interrupted' }, 'cancelled'],
-      [{ kind: 'error', step: 1, message: 'boom' }, 'end_turn'],
+      [{ kind: 'error', error: new Error('boom') }, 'end_turn'],
     ]
     for (const [reason, expected] of cases) expect(turnEndToStopReason(reason)).toBe(expected)
   })

packages/acp/acp/tests/turns.spec.ts

@@ -91,7 +91,7 @@ describe('ACP prompt lifecycle', () => {
       if (subject !== agent || message.source.kind !== 'user' || inserted) return
       inserted = true
       const source = { kind: 'plugin', plugin: 'test' } as const
-      agent.session.append('turn/start', { turn: 1, trigger: { kind: 'message', source } })
+      agent.session.append('turn/start', { turn: 1 })
       agent.session.append('user/message', createUserMessage({
         content: [{ type: 'text', text: 'autonomous work' }],
         source,