Parsing hours using single digit without separator gives invalid results

Trying to parse single digit hours doesn't work correctly when there is no separator character:

`dayjs("20240726 931", 'YYYYMMDD Hmm', true).isValid() // false, expected true`
`dayjs("931", 'Hmm', true).isValid() // false, expected true`
`dayjs("20240726 931", 'YYYYMMDD Hmm', true).hour() // 21, expected 9`

If there is a separator between H and mm then result is as expected:

`dayjs("20240726 9 31", 'YYYYMMDD H mm', true).isValid() // true, expected true`
`dayjs("9 31", 'H mm', true).isValid() // true, expected true`
`dayjs("9 31", 'H mm', true).hour() // 9, expected 9`

**Information**
- Day.js Version: v1.11.12
- OS: Windows
- Browser: Edge 127.0.2651.98
- Time zone: UTC +3 EEST (Eastern European Summer Time)

Reproduce the strict parsing examples for `H` and `Hmm`, comparing inputs with and without a separator, and inspect the date-format parsing entry points they exercise. Add regression coverage for single-digit hours without a separator; done means the examples are valid and return hour 9 as expected.

Written by the indexing model from the issue text.