[Bug]: LocalMemoryExecutionClient returns operations that have already checkpointed.

[zhongkechen]

Expected Behavior

checkpoint API returns only the new operations since last time checkpoint is called.

Actual Behavior

checkpoint API currently returns all operations in the history, which causing phasers in SDK to advance over the range:

{"@timestamp":"2026-02-13T00:05:23.125Z","ecs.version":"1.2.0","log.level":"DEBUG","message":"Advancing phaser 0 -> 1: java.util.concurrent.Phaser@c4a4e10[phase = 2 parties = 1 arrived = 0]","process.thread.name":"durable-sdk-internal-0","log.logger":"com.amazonaws.lambda.durable.execution.ExecutionManager"}
{"@timestamp":"2026-02-13T00:05:23.128Z","ecs.version":"1.2.0","log.level":"DEBUG","message":"Advancing phaser 1 -> 2: java.util.concurrent.Phaser@c4a4e10[phase = 3 parties = 1 arrived = 0]","process.thread.name":"durable-sdk-internal-0","log.logger":"com.amazonaws.lambda.durable.execution.ExecutionManager"}

Steps to Reproduce

enable logging for phaser and run the case testOperationTracking

SDK Version

0.5

Java Version

17

Is this a regression?

No

Last Working Version

No response

Additional Context

No response