fix(scheduler): scheduleName returns undefined when imported from ARN

[mazyu36]

Issue # (if applicable)

Closes #36361.

Reason for this change

When importing a schedule using Schedule.fromScheduleArn(), the scheduleName property returns undefined instead of the actual schedule name.

Description of changes

Fixed the ARN parsing logic in Schedule.fromScheduleArn() to correctly extract the schedule name from the resource path. AWS Scheduler ARNs have the format arn:aws:scheduler:region:account:schedule/GROUP/NAME, and the previous implementation only captured the group name.

Describe any new or updated permissions being added

No new or updated permissions.

Description of how you validated changes

Added unit tests to verify correct parsing and error handling.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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

[aws-cdk-automation]

The pull request linter fails with the following errors:

❌ Fixes must contain a change to an integration test file and the resulting snapshot.

If you believe this pull request should receive an exemption, please comment and provide a justification. A comment requesting an exemption should contain the text Exemption Request. Additionally, if clarification is needed, add Clarification Request to a comment.

✅ A exemption request has been requested. Please wait for a maintainer's review.

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[mazyu36]

Exemption Request: This change only fixes ARN parsing logic in a static import method and does not interact with AWS APIs. Unit tests fully cover the parsing logic and error handling.