Function createClient

Create a configured HTTP client.

Validates policy values at construction (the retry checks are owned by validateRetryPolicy, which HttpClient itself runs, so they hold however the client is built):

• retry.limit is a positive safe integer
• retry.delay and retry.maxRetryAfterMs are finite, non-negative, and within the maximum timer delay
• the largest exponential retry delay remains finite and timer-safe
• circuitBreaker.threshold >= 1
• rateLimit.maxRequests >= 1 and rateLimit.windowMs > 0

Defaults timing to createDefaultClientTiming() when omitted.