Fix wan T2V inference with larger batchsize than 1

[MoayedHajiAli]

Currently Wan2 T2V inference fails on batchsize larger than 1 due to

1. Incompatiable shape between the time conditioning and the modulation tensor
2. A bug in the text encoder that truncate the text to the smallest text token length available in the batch.

I introduced two small fixes but I am not sure if other inference/training behaviors are also affected (e.g I2V).