feat(session): persist optional time zones

packages/core/session/tests/fork.spec.ts

@@ -63,7 +63,9 @@ function inherited(session: Session): readonly SessionEvent[] {
 describe('SessionStore.fork', () => {
   it('forks an empty live session as an empty child with lineage metadata', async () => {
     const { ctx, sessions } = await setup()
-    const source = ctx.sessions.create(SessionId('empty-parent'), { meta: { cwd: '/workspace' } })
+    const source = ctx.sessions.create(SessionId('empty-parent'), {
+      meta: { cwd: '/workspace', timeZone: 'Asia/Shanghai' },
+    })
 
     const child = sessions.fork(source, undefined, SessionId('empty-child'))
 
@@ -71,11 +73,21 @@ describe('SessionStore.fork', () => {
     expect(child.header).toMatchObject({
       id: SessionId('empty-child'),
       cwd: '/workspace',
+      timeZone: 'Asia/Shanghai',
       parentSession: SessionId('empty-parent'),
       seedLength: 0,
     })
   })
 
+  it('keeps a headerless fork headerless', async () => {
+    const { ctx, sessions } = await setup()
+    const source = ctx.sessions.create(SessionId('headerless-parent'), { meta: { cwd: '/workspace' } })
+
+    const child = sessions.fork(source, undefined, SessionId('headerless-child'))
+
+    expect(child.header.timeZone).toBeUndefined()
+  })
+
   it('forks the latest completed boundary by default into detached frozen seed events', async () => {
     const { ctx, sessions } = await setup()
     const source = ctx.sessions.create(SessionId('parent'), { meta: { cwd: '/workspace' } })