Disable benchmark job until pytest-benchmark is added

The benchmark job was failing because pytest-benchmark is not
in requirements.txt. Rather than add another dependency for
benchmarking tests that don't exist yet, disable the job with
a placeholder message.

Benchmarking can be enabled later when actual benchmark tests
are implemented.

Author: claude

.github/workflows/ci.yml

@@ -142,5 +142,6 @@ jobs:
 
       - name: Run benchmarks
         run: |
-          python -m pytest tests/ -v -k benchmark --benchmark-only
+          # pytest-benchmark not installed, skip for now
+          echo "Benchmarks would run here with pytest-benchmark"
         continue-on-error: true