xl-agent benchmark: Cats Effect CPU starvation warnings during streaming

[arcaputo3]

Problem

When running benchmarks with --stream flag, Cats Effect emits repeated CPU starvation warnings:

WARNING: Your app's responsiveness to a new asynchronous event (such as a new connection, 
an upstream response, or a timer) was in excess of 100 milliseconds. Your CPU is probably 
starving. Consider increasing the granularity of your delays or adding more cedes. This may 
also be a sign that you are unintentionally running blocking I/O operations (such as File 
or InetAddress) without the blocking combinator.

This warning appears 80+ times during a single benchmark run.

Likely Cause

Blocking I/O operations (file reads, network calls) not wrapped in IO.blocking { ... } or IO.interruptible { ... }.

Areas to Investigate

1. File operations in benchmark runner - reading/writing Excel files
2. Network calls to Anthropic API - might need proper async handling
3. Process execution - running xl CLI commands

Files to Check

• xl-agent/src/com/tjclp/xl/agent/benchmark/ - Benchmark runner code
• xl-agent/src/com/tjclp/xl/agent/anthropic/ - API client code

Impact

• Performance degradation during benchmarks
• Potential timeout issues
• Not a correctness bug, but affects reliability

Context

Observed during SpreadsheetBench task 2768 with --parallelism 3 --stream flags.

[arcaputo3]

Closing — fixed via Dispatcher.sequential[IO] in CodeExecution.scala, which avoids blocking the CE compute pool.