fix(sdk): skip plugin hook work without plugins

[yaythomas]

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 #795

Description

When a checkpoint response changed an operation's status, onCheckpointComplete converted every stored operation for the operation change hook, even when no plugin was registered. So the cost of each checkpoint grew with the number of operations, and long sequential executions slowed down as they ran.

onCheckpointComplete now builds the change info and calls onOperationChange only when a plugin is registered. Plugins receive the same information as before.

Demo/Screenshots

Not applicable.

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. ExecutionManagerTest has two new tests.

• With no plugin registered, checkpointWithoutPluginsSkipsOperationChangeInfo checks that toOperationChangeInfo is never called. It also checks that every operation is stored and that a waiting operation completes. It fails without this change.
• With a plugin registered, checkpointWithPluginReportsEachStatusChangeOnce checks that onOperationChange fires once for each response that changes a status.

Integration Tests

Have integration tests been written for these changes?

No. The unit tests cover both paths. The existing onOperationChange tests in PluginIntegrationTest pass unchanged.

Examples

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

No. The change does not affect the public API.

[github-actions]

Codex AI review

No actionable findings. The guard preserves checkpoint updates and registered-plugin notifications, with focused regression tests for both paths. Residual test risk: tests were inspected but not executed, as required by the review constraints.

Reviewed commit de0c4541da506fc419dacfac373b395a7f5f700c. Workflow run