redactionMarker function
The repo-standard [REDACTED:<kind>] marker for kindLabel (the
marker contract documented in wire_protocol). ONE construction site:
the pipeline and the bash shape rewriter (issue #1408 AC3) must never
diverge — a divergent marker would slip past the pipeline's
re-redaction skip logic.
Implementation
String redactionMarker(String kindLabel) => '[REDACTED:$kindLabel]';