0.5.1

Added

• examples/aep/obligation.yaml, the tenth ladder — and the first written entirely in names no Rust enum holds. engineering-protocols 0.17.0 added obligation: a commitment on a clock nobody controls, open → met | slipped, where slipped opens on a date and met is terminal while slipped is not, because an obligation that slipped can still be met.

  The kind, all three of its rungs, and its dated guard needed no code in either repository. That is what the open-vocabulary work and the before/after operators were for, and it is the first thing to spend both at once.

  The equivalence test gained the matching half: a rung the pinned ladder dates must be dated here too, paired by (target status, frontmatter key). Without it a definition could quietly drop the after precondition and only the upstream document would still say the rung waits.

  scripts/check-upstream-pin.py found the drift by itself, again — second time in two waves.