perf: eliminate Func and closure allocation in DedicatedThreadExecutor

[TimothyMakkison]

Pass action into StartNew eliminating allocation of Func<TResult> and associated closure

Before

After

[thomhurst]

Summary

Eliminates closure and Func allocation in DedicatedThreadExecutor by passing action as a parameter to StartNew instead of capturing it.

Critical Issues

None found ✅

Suggestions

None - this is a clean performance optimization with measurable benefit in a hot path.

Verdict

✅ APPROVE - No critical issues

The static lambda + parameter passing approach correctly eliminates the closure allocation while maintaining the same behavior. The cast back to Func<ValueTask> is safe since we're passing the original typed parameter through StartNew's object state parameter.