89ef145254
The dashboard's POST /links is the fourth writer of link_tasks (CLI, tool, dashboard, plus the graph builder); return the same ``gated`` flag so every surface that can create the deadlock can see it. Document the ``dependency_wait`` payload the link path emits and the delegation rule the reporter derived (never link a support card under the card it unblocks). Drops the CLI output test (a change-detector on prose); the two DB-level invariants (event emitted on demotion / none for a done parent) stay.