Add directory-level explanation for GitHub repositories

[calchiwo]

Add the ability to generate an explanation for a specific directory inside a GitHub repository.

Example:

explainthisrepo facebook/react/packages/react-dom

Current behavior analyzes the entire repository. This change would allow analyzing a specific directory instead.

Implementation idea:

Detect paths in the form:

owner/repo/path/to/directory

Fetch directory contents using the GitHub API:

GET /repos/{owner}/{repo}/contents/path

Then analyze the returned file list and build a prompt describing the structure and purpose of that directory.

Example output:

This directory contains the React DOM renderer implementation. It includes the core logic responsible for rendering React components into the browser DOM and managing updates.

This would help developers quickly understand the role of specific parts of large repositories without analyzing the entire project.