refactor(agent): simplify inbox-driven turn admission

packages/client/runtime/tests/request-inspection.spec.ts

@@ -225,20 +225,15 @@ describe('inspectRequests', () => {
     const snapshot = inspectRequests(entriesOf([
       at(0, 'step/start', { turn: 1, step: 1 }),
       at(1, 'turn/end', {
-        turn: 1,
-        reason: {
-          kind: 'error',
-          step: 1,
-          failure: {
-            code: 'AUTH',
-            message: 'Authentication Fails, Your api key: sk-preview-secret is invalid',
-          },
+        turn: 1, step: 1, reason: { kind: 'error', error: {
+          code: 'AUTH',
+          message: 'Authentication Fails, Your api key: sk-preview-secret is invalid',
+        },
         },
       }),
       at(2, 'step/start', { turn: 2, step: 1 }),
       at(3, 'turn/end', {
-        turn: 2,
-        reason: { kind: 'error', step: 1, message: 'plugin exploded' },
+        turn: 2, step: 1, reason: { kind: 'error', error: 'plugin exploded' },
       }),
     ]))