Fix copy buttons in app on non-secure HTTP origins

[OpenCodeEngineer]

Summary

Copy buttons in the app web UI do not work when the app is served over plain HTTP (for example http://100.108.64.76:4096).

Problem

navigator.clipboard.writeText() requires a secure context in most browsers. On non-HTTPS origins, clipboard writes fail unless a fallback is used.

Scope

• Audit all copy button implementations in packages/app/src/
• Create/fix a shared clipboard utility with fallback support
• Ensure code block, assistant message, and terminal output copy actions all use it
• Validate with cd packages/app && bun typecheck

Notes

The likely fallback is document.execCommand("copy") using a temporary textarea appended to the DOM.

[OpenCodeEngineer]

Started investigation. Auditing all clipboard/copy implementations under packages/app/src/, with focus on HTTP fallback behavior and shared clipboard handling.

[OpenCodeEngineer]

Implementation delegated and applied locally. Reviewing the resulting clipboard utility changes and validating the affected app/UI copy paths before finalizing.

[OpenCodeEngineer]

During review I found the delegated branch also contained unrelated changes. I am resetting local work back to dev and retaining only the clipboard-related files needed for this HTTP copy fix.

[OpenCodeEngineer]

Clipboard fix is now isolated to the intended app/UI files only:

• packages/ui/src/components/copy-to-clipboard.tsx
• packages/ui/src/components/{markdown,message-part,text-field,tool-error-card}.tsx
• packages/app/src/{pages/session/use-session-commands.tsx,components/session/session-header.tsx}

Validation completed successfully:

• cd packages/app && bun typecheck
• cd packages/ui && bun typecheck

This addresses HTTP/non-secure origins by using an execCommand("copy") textarea fallback when navigator.clipboard.writeText() is unavailable.

[dzianisv]

Duplicate of #206.