KeyBuilder strips retry topics for a different consumer group

KeyBuilder.parseNormalTopic(topic, cid) strips every topic beginning with the retry prefix. If the topic belongs to another consumer group, it removes a prefix using the requested cid length and returns a corrupted topic; short regular retry topics can also throw. Expected behavior: strip only an exact POP retry prefix for the supplied consumer group.

Search for KeyBuilder.parseNormalTopic(topic, cid) and inspect how it recognizes retry topics and uses the consumer-group id. Add focused coverage for a different consumer group and a short regular retry topic, then verify that only an exact POP retry prefix for the supplied group is stripped.

Written by the indexing model from the issue text.