max_rpm was stored on the Agent but never wired to a runtime RateLimiter,
so ExecutionConfig(max_rpm=N) did not throttle requests. Now the Agent
auto-builds RateLimiter(requests_per_minute=N) when max_rpm is set and no
explicit rate_limiter is provided. Explicit rate_limiter still takes
precedence; max_rpm<=0 raises ValueError. YAML max_rpm now also wires a
live limiter.
Co-authored-by: Dhivya-Bharathy <[email protected]>
