Double tokio::spawn introduces unnecessary task scheduling overhead

[coderabbitai]

Problem

The current implementation uses double tokio::spawn calls, creating unnecessary task churn:
listener.accept() → spawn(process_stream) → inside process_stream another spawn(app.handle_connection)

Affected Locations

• Lines 341-342 in src/server.rs
• Lines 373-376 in src/server.rs

Current Code

tokio::spawn(async move {
    app.handle_connection(stream).await;
});

Suggested Improvement

Unless the inner spawn isolates crash-safety or blocking work, call app.handle_connection directly:

app.handle_connection(stream).await;

Benefits

• Reduces task scheduling overhead
• Simplifies the execution flow
• Eliminates one unnecessary context switch

Context

This is a performance optimization that reduces the complexity of the async task execution without affecting functionality.

References

• Pull Request: Implement preamble callback tests #28
• Review Comment: Implement preamble callback tests #28 (comment)

Reported by: @leynos