fix(otel): keep continuation spans within invocation

[zhongkechen]

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Issue Link, if available

Observed in the OpenTelemetry invocation-view conformance run: https://github.com/aws/aws-durable-execution-conformance-tests/actions/runs/31059801062/job/92519884437?pr=69

Description

Invocation-view continuation spans were backdated to the logical operation start timestamp from a prior Lambda invocation. Because the continuation is parented to the current invocation span, this made it start before its parent and overlap the original STARTED operation span.

Allow continuation spans to use their creation time in the current invocation. The execution-view plugin continues to use the original operation timestamp for its single logical cross-invocation span. The unit test now verifies that a continuation is parented to and temporally contained by the current invocation span.

Demo/Screenshots

Not applicable.

Checklist

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

Testing

Unit Tests

Updated InvocationOtelPluginTest with a regression test covering continuation span parentage and temporal containment.

Integration Tests

Ran mvn -pl otel-plugin -am test: reactor build succeeded, including all 148 OpenTelemetry plugin tests and 17 invocation plugin integration tests. No new integration test was needed for this isolated span timestamp change.

Examples

Not applicable.