copilot usage metrics

The copilot usage metrics tag covers reporting changes for GitHub Copilot in enterprise and organizational settings. Current coverage focuses on an updated metrics API that adds total merged pull requests by users in each AI adoption phase. This provides engineering leaders with a way to compare AI adoption with organizational throughput, rather than relying only on average user behavior. The coverage also places the new field in the broader context of evaluating whether AI coding tools affect delivery and supports more informed ROI discussions. These metrics do not independently prove business impact, but they offer a more concrete starting point for analyzing Copilot use across development teams.