Captures the dual representation we have today (legacy filesystem stage
strings + front-matter flags vs the typed Stage/ArchiveReason/ExecutionState
enums in pipeline_state.rs that are defined-but-not-wired) and itemises the
transitions and behaviours we have identified as missing or partially
implemented (first-class supersede/abandon/hold verbs, type-conversion side
effects, pinned-agent honouring under contention, blocked-flag enforcement
beyond auto-assign, ghost-story recovery, etc.).
Section (b) is intended as a living dumping ground — append new
transitions and incidents as they come up so that the state-machine
roadmap (spike 613 in backlog) has a ready-made input.
dave