docs(DOC-2012): narrow 4.x claim, fix unvalidated wording, tighten KIP-890

- Scope the 4.x compatibility claim to the Apache Kafka Java client per
  @mattschumpert's review note; other clients in the validated list have
  not been broadly re-validated at 4.x.
- Replace "unsupported client" with neutral phrasing to resolve the
  CodeRabbit terminology inconsistency vs the earlier "not validated"
  paragraph.
- Tighten the KIP-890 bullet from five sentences to three; move the
  epoch-bumping detail into a parenthetical so the bullet doesn't
  dominate the unsupported-features list visually.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Feediver1

modules/develop/pages/kafka-clients.adoc

@@ -18,7 +18,7 @@ Use this reference to:
 
 == Kafka client compatibility
 
-Clients developed for Kafka versions 0.11 or later are compatible with Redpanda, including Kafka 4.x clients. Modern clients auto-negotiate protocol versions or use an earlier protocol version accepted by Redpanda brokers.
+Clients developed for Kafka versions 0.11 or later are compatible with Redpanda. The Apache Kafka Java client at version 4.x is validated against Redpanda using the ducktape and chaos test suites; other clients in the table below have not been broadly re-validated at 4.x but remain compatible with the Kafka protocol versions they have always supported. Modern clients auto-negotiate protocol versions or use an earlier protocol version accepted by Redpanda brokers.
 
 TIP: Always use the latest supported version of a Kafka client.
 
@@ -51,7 +51,7 @@ a|
 
 Clients that have not been validated by Redpanda Data, but use the Kafka protocol, remain compatible with Redpanda subject to the limitations in the next section (particularly those based on librdkafka, such as confluent-kafka-dotnet or confluent-python).
 
-If you find an unsupported client, reach out in the https://redpanda.com/slack[Redpanda community Slack^].
+If you find a client that does not work with Redpanda, reach out in the https://redpanda.com/slack[Redpanda community Slack^].
 
 == Unsupported Kafka features
 
@@ -75,7 +75,7 @@ ifndef::env-cloud[]
 * Quotas per user for bandwidth and API request rates. However, xref:manage:cluster-maintenance/manage-throughput.adoc#client-throughput-limits[quotas per client and per client group] using AlterClientQuotas and DescribeClientQuotas APIs are supported.
 endif::[]
 +
-* https://cwiki.apache.org/confluence/display/KAFKA/KIP-890[KIP-890^] (Transactions Server-Side Defense): Redpanda does not implement the server-side portion of KIP-890. KIP-890 addresses a class of transaction errors specific to Kafka's replication model. Redpanda's Raft-based replication is not susceptible to this issue. When connecting to Redpanda, Kafka 4.x clients detect that Transactions V2 is not supported and fall back to the original transaction protocol. Per-transaction epoch bumping is part of Transactions V2 and does not apply in this case.
+* https://cwiki.apache.org/confluence/display/KAFKA/KIP-890[KIP-890^] (Transactions Server-Side Defense): Redpanda does not implement the server-side portion of KIP-890, which addresses transaction errors specific to Kafka's replication model. Redpanda's Raft-based replication is not susceptible to this class of errors. When connecting to Redpanda, Kafka 4.x clients detect that Transactions V2 is unsupported and fall back to the original transaction protocol (per-transaction epoch bumping is part of V2 and does not apply).
 
 If you find an unsupported feature or incompatibility, https://github.com/redpanda-data/redpanda/issues/new[file an issue^] with the Redpanda team.