feat: add file change tracking to session metrics (#6094)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/cli/src/ui/components/SessionSummaryDisplay.test.tsx

@@ -60,6 +60,10 @@ describe('<SessionSummaryDisplay />', () => {
         totalDecisions: { accept: 0, reject: 0, modify: 0 },
         byName: {},
       },
+      files: {
+        totalLinesAdded: 42,
+        totalLinesRemoved: 15,
+      },
     };
 
     const { lastFrame } = renderWithMockedStats(metrics);