mtmd: fix Granite4 Vision image sequence assembly (#26653)

* mtmd: fix granite 4v grid assembly

(cherry picked from commit 91f82eb1b489bff0dc3f649edf2cb9e0b7f656e9)

* mtmd: fix truncation for scaled image height and width before unpad

Signed-off-by: Hemanth Battu <hbattu@ibm.com>

* mtmd: remove MTMD_DUMP_EMBD debug scaffolding

Signed-off-by: Hemanth Battu <hbattu@ibm.com>

* clean up comments, clarify about anyres_info excluded from serialization

* add_newline is now dead code

---------

Signed-off-by: Hemanth Battu <hbattu@ibm.com>
Co-authored-by: Xuan Son Nguyen <son@huggingface.co>
Co-authored-by: Hemanth Battu <hbattu@ibm.com>

tools/mtmd/mtmd.cpp

@@ -891,10 +891,10 @@ struct mtmd_context {
                 } break;
             case PROJECTOR_TYPE_GRANITE4_VISION:
                 {
-                    img_beg = "<image>";
-                    img_end = "";
+                    // ... (image embeddings) \n ...
+                    img_beg = "";
+                    img_end = "\n";
                     image_preproc = std::make_unique<mtmd_image_preprocessor_granite>(ctx_v);
-                    ov_img_first = true;
                 } break;
             default:
                 throw std::runtime_error(string_format("%s: unexpected vision projector type %d\n", __func__, proj));