refactor(agent-loop): simplify message machine

packages/host/apiproxy/tests/api-proxy-blank.spec.ts

@@ -71,7 +71,7 @@ describe('summary blank = conversation not started', () => {
     const session = ctx.sessions.create()
     attach(session)
     appendStandalone(session)
-    session.append('turn/start', { turn: 0, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('turn/start', { turn: 0 })
     expect(await listBlank(api, session.id)).toBe(false)
   })
 })

packages/host/apiproxy/tests/api-proxy-projections.spec.ts

@@ -225,7 +225,7 @@ describe('session/projection push frame', () => {
 
     seedMessages(session, 1)
     // Same-reference apply: turn/start does not concern the unit — no frame.
-    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('turn/start', { turn: 1 })
     seedMessages(session, 1)
 
     const frames = await collected

packages/host/apiproxy/tests/api-proxy-view.spec.ts

@@ -83,7 +83,7 @@ describe('mux live view computation', () => {
     const rawResult = `RAW_RESULT:${'x'.repeat(64 * 1024)}`
 
     const session = ctx.sessions.create()
-    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('turn/start', { turn: 1 })
     session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-gen'), name: 'gen', arguments: '{}' })
     session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-term'), name: 'term', arguments: '{"cmd":"echo hi"}' })
     session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-diff'), name: 'diffy', arguments: '{}' })
@@ -146,7 +146,7 @@ describe('mux live view computation', () => {
     // history resolves the agent first; a live structural stub is enough (only
     // .session is read on this path).
     ctx.agents.register({ id: session.id, session, status: 'idle', ctx } as Agent)
-    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('turn/start', { turn: 1 })
     session.append('tool/call', { turn: 1, step: 1, callId: CallId('h-term'), name: 'term', arguments: '{"cmd":"ls"}' })
     // meta rides through to presentResult's ToolResult (the spread arm).
     session.append('tool/result', {
@@ -217,7 +217,7 @@ describe('mux live view computation', () => {
     const fiber = await ctx.plugin(Object.assign((inner: Context) => {
       session = inner.sessions.create('session-doomed' as SessionId)
     }, { inject: ['sessions'] }))
-    session?.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session?.append('turn/start', { turn: 1 })
     session?.append('tool/call', { turn: 1, step: 1, callId: CallId('c-doomed'), name: 'term', arguments: '{"cmd":"x"}' })
     // Disposing the owning fiber detaches the session mid-stream; the
     // session/disposed listener must clear its open-call table entry.
@@ -236,7 +236,7 @@ describe('mux live view computation', () => {
     const collected = collect(stream, 4, abort)
 
     const session = ctx.sessions.create()
-    session.append('turn/start', { turn: 1, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('turn/start', { turn: 1 })
     session.append('tool/call', { turn: 1, step: 1, callId: CallId('c-late'), name: 'term', arguments: '{"cmd":"tail"}' })
     session.append('turn/end', { turn: 1, reason: { kind: 'completed' } })
     // The turn/end above cleared the live table; pairing must fall back to

packages/host/apiproxy/tests/api-proxy-workspace.spec.ts

@@ -50,7 +50,6 @@ function stubAgent(session: Session): Agent {
     followup: () => {},
     steer: () => {},
     inject: () => {},
-    send: () => {},
     cancel() {},
     whenIdle: () => Promise.resolve(),
   }