docs: align sniff entries dict shape with data_hex/decoded fields

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -336,7 +336,7 @@ s.stop()                         # end the sniff (sends BREAK_LOOP)
 
 print(len(s.entries))            # all captured frames across pause/resume cycles
 print(s.state)                   # 'sniffing' | 'paused' | 'stopped'
-s.entries[0]                     # {'protocol', 'direction', 'duration', 'timestamp', 'data'}
+s.entries[0]                     # {'protocol','direction','duration','timestamp','data','data_hex','decoded'}
 s.close()                        # stop (if needed) and close the serial port
 ```