ax(mining): replace prose comment with usage example on ReduceHashrateHistory

AX Principle 2: comments must show HOW with concrete values, not restate
what the signature already says.

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

pkg/mining/miner.go

@@ -459,7 +459,7 @@ func (b *BaseMiner) GetLogs() []string {
 	return logBuffer.GetLines()
 }
 
-// ReduceHashrateHistory aggregates and trims hashrate data.
+// miner.ReduceHashrateHistory(time.Now()) // aggregates high-res points older than 5 min into 1-min low-res buckets; trims low-res to 24h
 func (b *BaseMiner) ReduceHashrateHistory(now time.Time) {
 	b.mutex.Lock()
 	defer b.mutex.Unlock()