clean-targets

Reclaim disk space by deleting cargo target/ build directories across the main checkout and every git worktree of this repo. Use whenever the user wants to clean up build artifacts, free disk space, run "cargo clean" everywhere, prune worktree build caches, or complains that the repo or its worktrees are eating gigabytes of disk. Safely skips any target dir that a running build or dev session (cargo, rustc, tauri…