isRetiredWorkBeadKey function
True when workBeadKey is a RETIRED session key — <bead>#rN or
<bead>#void-<sessionId>.
Authored against the two key-shape helpers in rework.dart
(reworkKeyFor / voidKeyFor) rather than re-deriving either grammar: a
retired key is exactly "carries a # suffix", and both shapes normalize to
the immutable base id.
Implementation
bool isRetiredWorkBeadKey(String workBeadKey) => workBeadKey.contains('#');