feat(session): persist optional time zones

packages/session/session-persistence-jsonl/tests/jsonl.spec.ts

@@ -786,6 +786,15 @@ describe('SessionPersistenceJsonl: scanLog unit', () => {
     expect(() => scanLog(Buffer.from(log))).toThrow(/session header/)
   })
 
+  it('round-trips an optional timeZone and rejects a non-string stored value', () => {
+    const zoned = meta('zoned-header', '/work', 'Asia/Shanghai')
+    const scanned = scanLog(Buffer.from(`${JSON.stringify(toHeaderLine(zoned))}\n`))
+
+    expect(scanned.meta).toEqual({ ...zoned, delegationDepth: 0 })
+    const invalid = { ...toHeaderLine(zoned), timeZone: 8 }
+    expect(() => scanLog(Buffer.from(`${JSON.stringify(invalid)}\n`))).toThrow(/session header/)
+  })
+
   it.each([
     ['missing', undefined],
     ['a string', '1'],