refactor(agent): simplify inbox-driven turn admission

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

@@ -91,7 +91,7 @@ describe('attached updatedAt excludes end-seed', () => {
     const resumed = ctx.sessions.create(sid('resumed-untouched'), {
       seed: [
         { type: 'turn/start', seq: 0, time: worked, data: { turn: 1 } },
-        { type: 'turn/end', seq: 1, time: worked, data: { turn: 1, reason: { kind: 'completed' } } },
+        { type: 'turn/end', seq: 1, time: worked, data: { turn: 1, step: 0, reason: { kind: 'completed' } } },
       ],
       meta: { cwd: '/proj', createdAt: 500 },
     })

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

@@ -54,7 +54,7 @@ function liveAgent(ctx: Context, id: string, turns: number, openTail = false): S
       content: [{ type: 'text', text: `prompt ${String(turn)}` }],
       source: { kind: 'user' },
     }), { surfaceOp: 'append' })
-    session.append('turn/end', { turn, reason: { kind: 'completed' } })
+    session.append('turn/end', { turn, step: 0, reason: { kind: 'completed' } })
   }
   if (openTail) {
     session.append('turn/start', { turn: turns + 1 })

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

@@ -62,7 +62,7 @@ function liveAgent(ctx: Context, id: string, turns: number): Session {
       content: [{ type: 'text', text: `prompt ${String(turn)}` }],
       source: { kind: 'user' },
     }), { surfaceOp: 'append' })
-    session.append('turn/end', { turn, reason: { kind: 'completed' } })
+    session.append('turn/end', { turn, step: 0, reason: { kind: 'completed' } })
   }
   ctx.agents.register({ id: session.id, session, status: 'idle', ctx } as Agent)
   return session

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

@@ -316,7 +316,7 @@ describe('mux live view computation', () => {
     const session = ctx.sessions.create()
     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' } })
+    session.append('turn/end', { turn: 1, step: 0, reason: { kind: 'completed' } })
     // The turn/end above cleared the live table; pairing must fall back to
     // scanning the session's in-memory events.
     session.append('tool/result', {

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

@@ -46,14 +46,11 @@ function stubAgent(session: Session): Agent {
     session,
     inbox: new Inbox(session, { inserted: () => {}, discarded: () => {} }),
     status: 'idle',
-    acceptsNextStep: false,
     ctx: new Context(),
     send: () => {},
     followup: () => {},
     steer: () => {},
     inject: () => {},
-    updateInbox: () => 'not-found',
-    reserveTurnAdmission: () => undefined,
     cancel() {},
     whenIdle: () => Promise.resolve(),
   }