zstanjj/HierSearch-Local-Agent · Improve model card: Add pipeline tag, library name, and usage example

This PR enhances the model card for the HierSearch-Planner-Agent by:

Adding the pipeline_tag: question-answering to improve discoverability for relevant tasks on the Hugging Face Hub.
Specifying library_name: transformers to indicate compatibility and enable the "how to use" widget.
Expanding the introductory section with a summary of the paper's abstract and key features.
Including a basic transformers code snippet for direct sample usage, leveraging the model's chat template.
Adding a clear citation section for proper attribution.

Please review and merge if these improvements are satisfactory.