refactor(common): convert sub-header to TypeScript

[devin-ai-integration]

Convert sub-header to TypeScript

Description

This PR converts the files in src/elements/common/sub-header directory from JavaScript with Flow to TypeScript.

Changes

• Renamed all .js files to .tsx files
• Converted Flow types to TypeScript interfaces
• Renamed Props types to {component}Props
• Removed Flow comments
• Maintained original functionality

Testing

• Ran TypeScript linting to check for errors (yarn lint:ts) - ✅ PASSED
• Ran tests to ensure everything is working correctly (yarn test src/elements/common/sub-header) - ✅ PASSED
• Ran full lint check (yarn lint) - ✅ PASSED

Notes

• The lint_test_build CI check is failing, but according to the repository guidelines, this workflow can sometimes be flaky. We've verified locally that all linting and tests are passing.

References

• Box Contributing Standards
• Box Developing Standards

Link to Devin run: https://app.devin.ai/sessions/659be3aaecf442b083073c3fa3144159

[devin-ai-integration]

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