124 unhandled effect branch

// ============================================================================
// Test 510_124: MUST_ERROR — a `!` decl branch left unhandled reports a
// missing EFFECT HANDLER, not a missing "continuation".
//
// `each` is declared `!` (effect — fires 0..N during the proc run) and `done`
// is `|` (terminal). The consumer handles `| done` but omits `each`. The
// kind belongs on the missing object: "continuation" is `|` spelling and
// sends the reader to the wrong remedy — a `| each` arm lands on KORU025
// (pinned by 510_100). `|` keeps the bare wording pinned by 510_109:
// "branch 'again' must be handled but no continuation found".
// ============================================================================

~pub tor tokenize { source: string }
! each string
| done usize

~tokenize(source: "x")
| done _ |> _