A legacy source column (todo/in-progress/...) validated moves only against the
closed VALID_TRANSITIONS map, which cannot know about a workflow-declared
column, so Todo -> Ideas was rejected even though the board drag pre-check and
context menu both offered it. Legacy sources now union VALID_TRANSITIONS with
the task's workflow-resolved adjacency, resolved lazily only when the legacy
table alone would reject. builtin:coding adjacency is unchanged.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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