feat(website): add copy and download buttons for sequences on details…

[theosanderson]

… page

Add SequenceActionButtons component that provides:

• Copy button to copy the sequence in FASTA format to clipboard with "Copied!" feedback
• Download button to download the sequence as a .fasta file

The buttons are displayed at the bottom of the sequence viewer on the sequence details page, using hydration-safe Button component to prevent flaky Playwright tests.

🚀 Preview: Add preview label to enable

[claude]

This PR resolves #5879 (Copy button and download button on sequences at bottom of details page)

[claude]

Claude finished @theosanderson's task in 1m 23s —— View job

---

Code Review Complete ✓

• Read and analyze all changed files
• Review code quality and best practices
• Check for security issues
• Evaluate performance considerations
• Review test coverage
• Check documentation
• Provide inline comments for specific issues
• Post final review summary

---

Summary

This PR successfully adds copy and download functionality for sequences on the details page. The implementation is generally solid and follows the project's guidelines for preventing flaky Playwright tests by using the hydration-safe Button component.

Strengths:

• Correctly uses the Button component to prevent race conditions in Playwright tests
• Clean component structure with clear separation of concerns
• Proper positioning with absolute positioning for the button container
• Good use of visual feedback (Copied! message)
• Appropriate test-id attributes for testing

Issues Found:
I've left inline comments on specific issues that should be addressed:

1. Silent error handling in clipboard operations - users won't know if copy failed
2. Potential memory leak in download function with synchronous cleanup of async operation
3. Missing filename sanitization that could cause issues with special characters
4. Minor inconsistency in variable naming between header and sequenceName

Testing:
The integration test change appears minimal (just fixing an ambiguous selector), but there are no new tests specifically for the copy/download buttons. Consider adding integration tests to verify:

• Copy button functionality and feedback message
• Download button creates correct file
• Buttons are properly disabled until hydration

Documentation:
No documentation updates needed for this user-facing feature, which is appropriate given the self-explanatory nature of the buttons.

Overall, this is a good implementation that needs a few refinements around error handling and edge cases before merging.

[anna-parker]

awesome! I tested it out a bit and the code looks good!