ax(mining): replace prose comment with usage example on LogBuffer.Clear

AX Principle 2: comments must show usage, not restate the signature.
"Clear clears the log buffer." adds zero information beyond the name.

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

pkg/mining/miner.go

@@ -84,7 +84,7 @@ func (lb *LogBuffer) GetLines() []string {
 	return result
 }
 
-// Clear clears the log buffer.
+// lb.Clear()  // called on miner Stop() to release memory
 func (lb *LogBuffer) Clear() {
 	lb.mu.Lock()
 	defer lb.mu.Unlock()