fix(text): allow boilerplate at both top and bottom

[VolodymyrLinuxovich]

Description

Closes #2469

Boilerplate at both the top and bottom of a document was not removed. The helper now accepts a run at the top, a run at the bottom, or both. Added tests.

Checklist

• I am familiar with the Contributing Guide.
• New or Existing tests cover these changes.
• The documentation is up to date with these changes.

[copy-pr-bot]

This pull request requires additional validation before any workflows can run on NVIDIA's runners.

Pull request vetters can view their responsibilities here.

Contributors can view more details about this message here.

[greptile-apps]

Confidence Score: 5/5

[Medium risk] Changes boilerplate detection logic in text processing.

The PR appears safe to merge; no actionable issue was identified.

Summary

The PR allows the boilerplate modifier to remove separate runs at both the top and bottom of a document, and adds helper and modifier tests for the behavior.

_{Reviews (1) · Last reviewed commit: "fix(text): allow boilerplate at both top..."}