069 reject undischarged string obligation

// Test (negative): a `[]const u8<unsanitized!>` value passed into any event
// that doesn't accept `<!unsanitized>` is rejected by the phantom checker.
//
// This is the taint-tracking shape: a tainted string flowing into a sink
// (like `std/io:print.ln`) without going through a sanitizer is a
// compile-time error. The phantom checker treats the obligation on the
// primitive payload exactly as it treats `*File<opened!>` — undischarged
// at scope exit is a rejection.
//
// Positive twin: 330_068.

import std/io

pub tor get-input {} -> string<unsanitized!>

get-input -> "user input data"

get-input(): s |> std/io:print.ln(s)