Paths are shown with a forward slash

Every path string ral produces, a value a builtin returns or text a person or the model reads, is /-separated on every host: C:/blah/bleh, //server/share/x, src/x/f. core::path::show::shown is the one place that shows a path; fold_for is its separator fold.

• One value on every host. A script’s glob or cwd yields the same string on Windows as on Unix, so a test or a model prompt need not know the host.
• Escapes cannot eat it. In a "…" literal \n is a newline; a C:\new printed back and pasted would be corrupted. / is inert there.
• Input already reads either. The resolver accepts both separators, so showing with / loses nothing.
• The verbatim exception. A \\?\C:\… head is dropped (dunce::simplified) where the path means the same without it. A path only the OS can read literally (\\?\UNC\…, \\.\pipe\…, a long or reserved-name verbatim path) is shown exactly as given, since / is not a separator there: show asks lex::parse_bytes under Windows rules (Parsed::has_os_namespace_head), the backslash-only HeadSpelling reading of a namespace head the OS hands back.
• The echo exception. A command head written as a path (.\build.cmd, C:\tools\x) is shown as the user typed it, not folded: Head.shown in core/src/runtime/command/head.rs echoes the word the user wrote, since the refusal answers that word. It is the one shown path not produced by shown; a ~ head is still shown through TildePath::shown.
• The native boundary. A path ral hands to the OS (PWD, sandbox rules, DACL calls, internal identity and matching) stays native. Only the text ral shows is folded.

On Unix shown is the identity.

Enforcement

clippy.toml bans Path::display, Path::to_string_lossy, Path::to_str, OsStr::to_string_lossy and OsStr::to_str, each naming shown as the replacement. A conversion that is genuinely native (a path handed to the OS, an env value, a non-UTF-8 check) takes a scoped #[allow(clippy::disallowed_methods, reason = "native: …")], so every site that does not show a path is a reviewed one.