According to these two references, non-residents would not qualify:
https://www.savingforcollege.com/529-plans/connecticut/connecticut-higher-education-trust-chet
https://www.thebalance.com/connecticut-tax-deductions-for-education-expenses-795319
In most states, the rule for part year residents is that the contribution must have been made during the time you were a resident. You may want to contact the CT Dept. of Revenue for a direct answer.
