What is the ruling on delaying exiting the state of Ihram and cutting the hair until after the Days of Tashreeq, then doing so outside the Haram and in regular clothes?

If you have cast the Jamrat al-Aqaba, performed the Tawaf al-Ifadah, and performed the Sa'i — if Sa'i was required of you — then you have achieved the first stage of tahallul (partial release from ihram restrictions). At this point, everything that was prohibited by ihram becomes permissible for you, except for intimate relations with women. There is no harm in remaining in your ihram garments, delaying the shaving or cutting of hair, traveling to Jeddah, and then wearing normal clothes to achieve complete tahallul. Shaving or cutting hair on the day of Eid is not a condition. Remaining in ihram garments until the completion of all rituals is permissible, and wearing tailored clothes before shaving or cutting hair is also permissible.