TTL cache invalidateAll loses to an in-flight async load

A Swift @MainActor cache with value(for:load:) that does let v = try await load(); entries[key] = v re-stores a stale value if invalidateAll() runs during the await (actor reentrancy). To prove it, hold the loader on a CheckedContinuation, call invalidateAll, resume the loader, then query again with a loader that returns a new value: the old value comes back. Fix: a generation counter bumped by invalidateAll, captured before the await and checked before storing. Separately, to verify that user-typed paths never execute on a remote shell, extract the real quoting helpers into a standalone swiftc binary, emit the exact commands for hostile filenames ($(), backticks, ;, quotes, glob, leading dash, non-ASCII) and run them under sh, bash and zsh, checking for sentinel files.