datetime: can't parse '%Y%m'

./src/tarantool -i
Tarantool 3.7.0-entrypoint-160-gbd9d8e9020
type 'help' for interactive help
tarantool> datetime = require('datetime')
---
...

tarantool> datetime.parse( datetime.new():set({year=2026, month=1}):format('%Y%m'), {format = '%Y%m'} )
---
- error: 'builtin/datetime.lua:898: could not parse ''202601'' using ''%Y%m'' format'
...

In contrast Python3:

import datetime as dt
>>> dt.datetime.strptime('202601', '%Y%m')
datetime.datetime(2026, 1, 1, 0, 0)

Reproduce the datetime.parse call shown in the issue, then inspect builtin/datetime.lua around line 898, where the reported error originates. Trace how %Y%m is handled against the formatted value 202601; done means parsing that format succeeds with the expected January 2026 value while existing behavior remains intact.