This adds a "clone agent" workflow so a project can have multiple independent working copies (separate git clones) as sibling directories, without forcing users to move existing repos.

What’s included

• Backend add_clone command: git clone into a chosen copies folder, inherit the project group, spawn an app-server session, and persist the workspace.
• Settings: per-project copiesFolder stored on WorkspaceGroup and editable in the Settings UI.
• UI: "New clone agent" action + modal to pick copy name and copies folder (with a suggested path + copy-to-clipboard).

Quality / safety fixes in this series

• Prevent double-submit via Enter while cloning.
• Prevent closing clone/worktree modals via backdrop/Escape while busy.
• Roll back and clean up if clone session spawn or persistence fails (including killing spawned session).
• Use async tokio::fs::remove_dir_all in async cleanup paths.
• Improve long-path usability in the modal (horizontal caret navigation) while hiding scrollbars.
• Speed up thread list matching for new workspaces by normalizing cwd paths and using a larger page size.

Testing

• npm run lint
• npm run typecheck
• cargo test (in src-tauri/)

Notes

• Existing worktree agents continue to work; clones introduce additional main workspaces.