fix: failed to enable lazy compilation in some cases

[chenjiahan]

Summary

Fix a regression introduced by #5431

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

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[Copilot]

Pull Request Overview

This PR fixes a regression in the lazy compilation plugin by streamlining the control flow to ensure lazy compilation is enabled correctly.

• Added an early return to skip further configuration when only imports are enabled
• Removed the old else block and unindented the main experiments call for clarity

Comments suppressed due to low confidence (1)

packages/core/src/plugins/lazyCompilation.ts:32

• Add a unit test for the case when options.imports is true to verify that lazyCompilation is skipped as intended by the early return.

          return;