Motivation

This follows up on #26455 to address three remaining producer send-failure cases. An oversized message serialized after schema registration can be cleaned up twice if its failure callback closes the producer during reconnect. A rejected chunk write can leave the send loop building subsequent chunks after the message has already failed, causing repeated callbacks and buffer releases. Interrupting a blocking chunked send also leaves references held for chunks that were never created.

Modifications

• Separate message-size validation from failure completion and remove failed deferred operations from the pending queue before invoking callbacks.
• Centralize failed-operation cleanup and ensure command release and operation recycling run even if a callback throws.
• Recheck the connection, epoch, and producer state throughout pending-message recovery, including after the last callback. Cover both size and schema failures while preserving connection cleanup on close.
• Stop building chunks after an operation fails and release the payload, memory reservation, permits, and context references belonging to unbuilt chunks.
• Release unbuilt chunk context references when a blocking send is interrupted, and document the locking, lifetime, and callback contracts.
• Extend ProducerMemoryLeakTest with real broker/client paths, deterministic event-loop task rejection, thread interruption, and callback-triggered close after a broker schema rejection.

Verifying this change

• Make sure that the change passes the CI checks.

(Please pick either of the following options)

This change is a trivial rework / code cleanup without any test coverage.

(or)

This change is already covered by existing tests, such as (please describe tests).

(or)

This change added tests and can be verified as follows:

(example:)

• Added integration tests for end-to-end deployment with large payloads (10MB)
• Extended integration test for recovery after broker failure

Does this pull request potentially affect one of the following parts:

If the box was checked, please highlight the changes

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment