I didn't get what u mean by waqf. Btw sukran shouldn't be pronounced as shukraa because it has a tanween تنوين which makes us pronounce the letter ن at the end of it. And انت may be pronounced as anta and anti and that depends on the tashkel تشكيل of the word likeأنتِ is pronounced as anti because it has kasra كسرة and أَنتَ is pronounced as anta because it has a fatha.

simply it is a common mistake to pronounce it Shukran it should be Shukra and the same with Anti it should be Ant. we have an important rule in Arabic tells us that we can't stop with a vowel. "My Spanish skills are rusty " means لغتى الأسبانية ضعيفة

As you know the last letter of the word loses its tashkeel if you stop speaking. This applies to modern classic Arabic and not dialects. This rule works with أنتِ but شكرًا has something different as it is said that way with tanween so often and when you say "قال لي شكرًا " means he said to me thanks but skokra without tanween will sound as he said to me (some) thanking .Hope it is helpful. Not to be mistaken! Shokran loses its tanween if it is not an extract from a conversation.for example أرسل لك شكرًا and of course state of الرفع والجر مثل " لا أحتاج الى شكرٍ" او "جاء منه شكرٌ"