Summary

Fix clipboard operations when navigator.clipboard is unavailable or rejects the write, such as on non-secure HTTP origins.

• use the Clipboard API when available
• fall back to a temporary textarea and document.execCommand("copy")
• remove the temporary element after every fallback attempt
• keep existing copied-state and error behavior unchanged
• replace unsafe direct clipboard calls across Workspace, Go Web, Studio, and Launcher

Testing

• clipboard regression tests: 5 passed
• Go Web production build passed
• Workspace production build passed
• Studio production build passed
• Launcher production build passed
• manually verified fallback copying in Chrome on a non-secure HTTP origin

Fixes #444