Extend the topology-runs list route with an optional loop_id filter that
returns iterations for a single loop, newest-iteration-first. Adds the
iteration and finished_at columns to the summary (skip-null on the JSON
so compares stay compact). Backed by list_by_loop in the repo, which uses
the existing topology_runs_loop_idx partial index.
LoopsCanvas fetches the runs in parallel with the loop detail and renders
an iteration timeline card (iteration #, status pill, start time, duration,
run id prefix) between the graph section and the actions row.
