Task 1.3 (Req 2.1, 2.2, 2.4).
- seed.pair_lessons derives obligation shapes for absence-mechanism rows
and falls back to the sink shape when no obligation is learned, so the
flow store is unchanged; skip reasons name the accepted dischargers.
- append_from_pair accepts both shape families (guard carries the
discharger kind); search_tree ignores obligation rows;
obligation_mechanisms selects them.
- Measured on vibe-py: the two vampi pairs seed protected_read /
identity_constraint / authenticated_context.
Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG
