Decline Spam Suggestion

A human looked at Rooster's 'suggest_spam' triage card and disagrees. Leaves the ticket exactly as it was -- an ordinary ticket to be worked, Frederick's own words (build task 2026-08-11): "Decline leaves it as an ordinary ticket to be worked" -- and only clears the suggestion off the desk (action_items.dismiss, "this does not need doing").

Gated the SAME way mark_spam above is -- ticket-kind grant or assignee (_require_kind_grant_or_assignee) -- deliberately NOT platform:action_items:write, the grant the generic POST /api/platform/action-items/{id}/dismiss route requires. That grant is bound to the Customer Service (b2c) role but not Account Manager (migrations/0046_ticket_access_by_role.sql), so routing this specific click through the generic endpoint would leave a b2g account manager able to AGREE with a suggestion (mark_spam only ever checked the ticket grant) but not decline one on the same ticket. Both halves of one gesture must open to the same person.

A missing/already-resolved card is a no-op, not an error -- the same "a double click, or someone else got there first, must never surface as a failure" tolerance mark_spam's own resolve_action_item_id branch documents just above.