The per-agent web UI todos flyout (loose-ends v2) had no mark-done
affordance at all — dismissing a todo was only possible via the
cancel_loose_end MCP tool, one id at a time. Add a checkbox per row,
a select-all/select-none/mark-done bulk row, and a new
POST /api/todos/mark-done handler that loops the existing single-id
MarkTodoDone request over the in-agent socket (no new wire request
type needed — the todos list is small, so N same-host round-trips is
cheap).
Fixes#2917
41c1b1a3fb