fix(schedule): close absolute-time review gaps

packages/schedule/tool-schedule/src/domain.ts

@@ -201,7 +201,7 @@ function parseOffsetInstant(value: string): number {
   if (groups === undefined) {
     throw new ScheduleInputError(
       'invalid_rule',
-      'at must be a strict RFC 3339 date-time with an explicit Z or numeric offset.',
+      'at must use YYYY-MM-DDTHH:mm:ss with optional 1-3 digit fractional seconds and an explicit Z or numeric offset.',
     )
   }
   const parts: CalendarParts = {

packages/schedule/tool-schedule/src/types.ts

@@ -29,7 +29,7 @@ export interface AtScheduleRecord {
   readonly id: ScheduleId
   /** Rule discriminator for an absolute one-shot reminder. */
   readonly kind: 'at'
-  /** Trimmed user-authored reminder content. */
+  /** Trimmed reminder content supplied at creation. */
   readonly prompt: string
   /** Four-digit-year RFC 3339 UTC target. */
   readonly scheduledAt: string

packages/schedule/tool-schedule/tests/tools.spec.ts

@@ -230,8 +230,25 @@ describe('Schedule tool protocol', () => {
     ])
     const changes = test.agent.session.events
       .filter(event => event.type === 'schedule/change' && event.data.operation === 'create')
-    expect(changes[0]?.data).not.toHaveProperty('at')
-    expect(changes[0]?.data).not.toHaveProperty('time_zone')
+    expect(changes.map((change) => {
+      if (change.type !== 'schedule/change' || change.data.operation !== 'create') {
+        throw new Error('expected only Schedule create changes')
+      }
+      return change.data.schedule
+    })).toEqual([
+      {
+        id: 'schedule-1',
+        kind: 'at',
+        prompt: 'join meeting',
+        scheduledAt: '2026-08-06T01:00:00.000Z',
+      },
+      {
+        id: 'schedule-2',
+        kind: 'at',
+        prompt: 'local meeting',
+        scheduledAt: '2026-08-07T01:30:00.000Z',
+      },
+    ])
   })
 
   it('returns stable at validation errors after persistence preflight', async () => {
@@ -240,7 +257,7 @@ describe('Schedule tool protocol', () => {
       prompt: 'bad instant', at: '2026-08-06T09:00:00',
     }))).toEqual({
       code: 'invalid_rule',
-      message: 'at must be a strict RFC 3339 date-time with an explicit Z or numeric offset.',
+      message: 'at must use YYYY-MM-DDTHH:mm:ss with optional 1-3 digit fractional seconds and an explicit Z or numeric offset.',
     })
     expect(value(await execute(test, 'schedule_create', {
       prompt: 'bad zone', at: { date: '2026-08-06', time: '09:00:00', time_zone: 'CST' },