[techartdev]

Clipboard uploads and remote copies previously failed whenever a destination name existed, even if the user wanted to replace it. Explorer also refused to delete folders containing files.

• Review destination collisions before transfer with Yes, Yes to all, or Cancel. Matching folders merge; destination-only files remain. Regular files use revision-checked atomic replacement on compatible OpenSSH SFTP hosts. Unsupported providers still refuse replacement safely.
• Let users explicitly opt in to deleting folder contents, including nested folders. Delete links as links, stop after the current item, and report partial completion if an operation fails.
• Cover replacement, folder merging, cancellation, and recursive deletion.

Validation: 413 source tests, 39 transfer tests, 59 SSH-core library tests, TypeScript build, and Vite production build passed. The broad Rust app suite has three existing workspace profile fixture failures outside the changed paths; the broad Vitest command also includes unrelated .local database test copies with no Vitest suites.