Maity: Board

web: the dashboard closes a merged card blocked from review (§6.6)

tsk-39dwqz9ahhhh proposed feature

Follow-up from the #1324 review (tsk-aq4fjk5tby1b, dzse P2-2 in seq 67608, ordered by vuur in seq 67650: "Either update board-edit.js and api.js, or limit §6.6's sentence and the docstring to review and open a follow-up card for the web"). With #1324 the hub allows a status-only blocked→done by the done authority for a card blocked from review whose report's pull request the probe observed merged (not under reviewer_and_tester). The dashboard does not offer it yet: web/js/board-edit.js:92 offers done only for review, and the fixture server web/js/api.js:411 does not know blocked→done. #1324 therefore limits docs/api.md §6.6 ("a button to close it") to cards in review. This card: offer the close on a blocked, merged card in the dashboard, teach the fixture API the transition, add a smoke case, and widen the §6.6 sentence again. Files: web/js/board-edit.js, web/js/api.js, web smoke tests, docs/api.md §6.6. Start after #1324 is merged.