Add web URL display to graph command for GitHub issues search

[Copilot]

Currently the graph command shows contribution statistics but doesn't provide an easy way to view the same results in the GitHub web interface. This PR adds a web URL link that points to the GitHub issues search page with the same query parameters.

Changes

• Added buildWebURL() function that generates properly encoded GitHub search URLs
• Modified handleGraphCommand() to display the web URL after the summary statistics
• Uses GitHub's web search syntax with proper URL encoding
• Added comprehensive tests for the new functionality

Example Output

After running gh contrib graph username, the output now includes:

Total Contributions: 5 over 30 days (avg: 0.17 per day)
PRs: 2 total (1 closed, 1 open)
Issues: 3 total (2 closed, 1 open)

View issues in GitHub: https://github.com/issues?q=is%3Aissue+org%3Agithub+author%3Ausername+sort%3Aupdated-desc+created%3A%3E2025-06-15

The URL respects all the same filters as the API query:

• Organization scope (org:github)
• Author filter (author:username)
• Date filtering when --since flag is used (created:>YYYY-MM-DD)
• Issue type filtering (is:issue)

Testing

• All existing tests continue to pass (17/17)
• Added TestHandleGraphCommand_WebURL to verify URL generation in integration
• Added TestBuildWebURL to test the URL building function in isolation
• Manually verified URL encoding and GitHub search compatibility

Fixes #3.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[maxbeizer]

@copilot let's not limit this to just issues. Please remove is:issue from the search string

[Copilot]

Removed is:issue filter from the search string. The web URL now includes both issues and pull requests. Updated display text to "View in GitHub:" and added tests to verify the new behavior. (commit b18cddc)