feat: Use per-context replay status

[ayushiahjolia]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Issue Link, if available

Fixes #383

Adds per-context replay tracking to the Java SDK. This is a prerequisite for the plugin hooks feature (#364) and OTel integration (#333).

Problem

Log suppression during replay used the global ExecutionManager.isReplaying() flag. When multiple branches run concurrently (parallel/map), the global flag flips to EXECUTION as soon as any branch encounters new work - causing logs in other branches that are still replaying to leak through.

The old per-context field (BaseContextImpl.isReplaying) was a one-shot transition guard used only by BaseDurableOperation.execute(). It was never used for log suppression and answered a different question ("has this context ever seen a non-cached op?") rather than ("is the next operation already checkpointed?").

Solution

Added proactive per-context replay tracking in DurableContextImpl:

• replayMode field - initialized by checking if the next operation (via peekNextOperationId()) exists in checkpoint storage
• updateReplayStatus() - called after nextOperationId() in each operation method; peeks at the following operation and transitions out of replay if it doesn't exist
• isReplayingContext() - exposes the per-context replay status to the logger and future plugin hooks

This matches the Python SDK's _track_replay() pattern: after consuming the current operation's ID, peek at the next one - if it's not in storage, we're past the replay boundary.

Checklist

• I have filled out every section of the PR template
• I have thoroughly tested this change

Testing

Unit Tests

Have unit tests been written for these changes? Yes

Integration Tests

Have integration tests been written for these changes? N/A

Examples

Has a new example been added for the change? (if applicable) N/A

[SilanHe]

is this intended?

[ayushiahjolia]

Yes, intentional. The default returns false (don't suppress) which is the safe default. Only DurableContextImpl overrides it with actual replay tracking. The only other subclass is StepContextImpl, whose user function only runs during real execution - so its logs should never be suppressed.

[zhongkechen]

removing an existing method would be a breaking change. We'll need a major version upgrade if we really want to remove this.

[ayushiahjolia]

Can mark it as deprecated and remove in future.

[zhongkechen]

I think this change is no longer required by our plugin interface and the OTel plugin as we are going to switch to a backend based approach.

[ayushiahjolia]

Closing this PR, this will be fixed by #435