ax(mining): replace prose comments with usage examples in ratelimiter

AX Principle 2: comments show HOW with real values, not prose descriptions.
cleanupLoop and cleanup had restatement comments; converted to call-site examples
matching the pattern used throughout the file.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/ratelimiter.go

@@ -39,7 +39,7 @@ func NewRateLimiter(requestsPerSecond, burst int) *RateLimiter {
 	return rl
 }
 
-// cleanupLoop removes stale clients periodically
+// go rl.cleanupLoop()  // started by NewRateLimiter; runs until rl.Stop()
 func (rl *RateLimiter) cleanupLoop() {
 	ticker := time.NewTicker(time.Minute)
 	defer ticker.Stop()
@@ -54,7 +54,7 @@ func (rl *RateLimiter) cleanupLoop() {
 	}
 }
 
-// cleanup removes clients that haven't made requests in 5 minutes
+// rl.cleanup()  // called every minute by cleanupLoop; evicts IPs idle for >5 minutes
 func (rl *RateLimiter) cleanup() {
 	rl.mu.Lock()
 	defer rl.mu.Unlock()