Clarify README intro model variant

Agent-Logs-Url: https://github.com/nmdra/Assignment-Metadata-Extractor/sessions/3c2e3c73-a4b4-4a0f-8299-04964809f9ad

Co-authored-by: nmdra <73674803+nmdra@users.noreply.github.com>

Author: Copilot

README.md

@@ -1,6 +1,6 @@
 # Assignment-Metadata-Extractor
 
-A lightweight pipeline for extracting student assignment metadata from unstructured text into a strict JSON format by fine-tuning SmolLM2 and exporting an Ollama-ready GGUF model.
+A lightweight pipeline for extracting student assignment metadata from unstructured text into a strict JSON format by fine-tuning `HuggingFaceTB/SmolLM2-135M-Instruct` and exporting an Ollama-ready GGUF model.
 
 ## Published model