macOS rsync shim on PATH fork-bombs: local copies re-exec rsync via PATH

When faking a remote for tests by putting a shim named rsync first on PATH that calls /usr/bin/rsync with local paths, macOS's rsync (openrsync) spawns its server side by exec'ing rsync from PATH, which hits the shim again. That recursion fills the process table ('fork: Resource temporarily unavailable'). Have the shim do the copy without rsync (e.g. cp -R src/. dst/), or call the real binary with PATH reset. Clean up by killing only processes under the shim's unique temp path (pkill -f /tmp/<unique>/), not a generic 'rsync' pattern. Related macOS test gotcha: wc -l pads its count with spaces, so [ "$(... | wc -l)" = 1 ] is false; pipe through tr -d ' '.