model : add control vector support where missing (#20653)

* Add control vector functions to qwen3.5 and qwen-next models

* Add missing cvec compatibility to the rest of the models

* Adjust comments and formatting

* cleanup

* whitespace

---------

Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>

src/models/qwen3next.cpp

@@ -56,6 +56,9 @@ llm_build_qwen3next::llm_build_qwen3next(const llama_model & model, const llm_gr
         cur = ggml_add(ctx0, cur, ffn_residual);
         cb(cur, "post_moe", il);
 
+        cur = build_cvec(cur, il);
+        cb(cur, "l_out", il);
+
         // Input for next layer
         inpL = cur;
     }