GitHub web UI lacks visible navigation to commit history

### Issue

The GitHub.com web interface does not provide an obvious or easily discoverable link to view a repository's commit history from the main repository page. Users looking to see contributions or recent changes must either:
- Know and type the direct URL manually (e.g., `/commits`)
- Search through sidebar menus
- Use keyboard shortcuts or browser find functions

### Context

When attempting to find how to view all contributions to a repository through the standard GitHub UI, there is no clear "Commits" or "History" button or link in the main header navigation or file browser area. This discoverability issue affects user experience, particularly for those new to GitHub or unfamiliar with direct URL navigation patterns.

### Expected Behavior

A clearly visible link or button (labeled "Commits," "History," or similar) should be accessible from:
- The main repository navigation header
- The file browser area
- Or prominently displayed in the repository sidebar

This would allow users to quickly access commit history without extra effort or knowledge of GitHub's URL structure.

### Additional Notes

- Encountered while using GitHub's Copilot Chat interface
- May impact user onboarding and general repository navigation
- Related to overall UI/UX design of the repository view

No repository files or tests are named. First verify whether this repository can change GitHub.com's UI, then inspect the repository navigation header, file browser area, and sidebar described in the report. Done means a visible, discoverable path to commit history is defined and implemented in the appropriate project.

索引モデルが issue の本文から書いたものです。