Improve validation to follow TextEmbedder pattern and clarify error messages

Co-authored-by: meilame-tayebjee <114609737+meilame-tayebjee@users.noreply.github.com>

Author: Copilot

torchTextClassifiers/model/components/text_embedder.py

@@ -299,19 +299,19 @@ def __init__(self, config: TextEmbedderConfig):
         )  # Group Query Attention (GQA): duplicate key/value heads to match query heads if desired
 
         # Validate head configuration
-        if self.embedding_dim % self.n_head != 0:
+        self.head_dim = self.embedding_dim // self.n_head
+        
+        if self.head_dim * self.n_head != self.embedding_dim:
             raise ValueError(
                 f"embedding_dim ({self.embedding_dim}) must be divisible by n_head ({self.n_head}). "
-                f"Got head_dim = {self.embedding_dim / self.n_head}"
+                f"Got head_dim = {self.head_dim} with remainder {self.embedding_dim % self.n_head}"
             )
 
         if self.n_head % self.n_kv_head != 0:
             raise ValueError(
                 f"n_head ({self.n_head}) must be divisible by n_kv_head ({self.n_kv_head}) for Group Query Attention. "
-                f"Got n_head / n_kv_head = {self.n_head / self.n_kv_head}"
+                f"Got remainder {self.n_head % self.n_kv_head}"
             )
-        
-        self.head_dim = self.embedding_dim // self.n_head
 
         self.label_embeds = nn.Embedding(self.num_classes, self.embedding_dim)