Converge an outstanding check (Lane B)

Manual convergence for a human-selected outstanding check (vendors/1099 plan, Phase 3, Section 8.3). Claims the unposted withdrawal feed row against the check's journal entry with the widened matcher, excludes the originally created register row, assigns the surviving feed row the entry's counterpart account, and marks the vendor_check cleared with cleared_via human_selected — atomically, in one transaction. The check must still be recorded, on the withdrawal's bank account, and within $1 of the withdrawal amount. Requires the post:entries role and the bank_transactions:read_write scope.