buffbench: switch main.ts to base2-free-opencode-kimi

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jahooma

evals/buffbench/main.ts

@@ -11,7 +11,7 @@ async function main() {
   // Use 'external:opencode' for OpenCode CLI
   await runBuffBench({
     evalDataPaths: [path.join(__dirname, 'eval-codebuff.json')],
-    agents: ['base2-free-opencode-minimax'],
+    agents: ['base2-free-opencode-kimi'],
     taskConcurrency: 6,
     saveTraces,
   })